Oni
Well, here comes my ultimate Oni guide. Why should you read mine and not someone else's? Just because I've beaten this game so many times, that I know exactly the best way for almost every situation. This is still under construction, though, so come back for more things.


Moves

Oni has a whole variety of moves. Basically, you need these keys: A, S, D, and W for movement, Shift for crouch/slide, Spacebar for jump, Ctrl for interact, and Left and Right mouse buttons for punches and kicks. The movements are easy. ASDW, a la Half Life, are strafe left, back, strafe right, and forward. Combinations are accepted. The most useful one of them is double-W, which makes you dash (run fast and loud). Of course the easiest move is block: to block, face the opponent, and don't move/punch/kick. You can crouch.

Space is your good ol' jump, it works if you want to just jump a little. Note: you can't jump if you are standing RIGHT in front of a crate because of a bug. You'll float for about a second without going up or down.

Shift is duck and crouch. Shift+W, A, or D will make you roll forward or sideways, Shift+W is a backward cartwheel. When dashing, Shift+W is a slide, which will get you really low and will act as a kick if you slide into a person.

Shift + Space makes a somersault in the air. (Notice that you have to jump first, otherwise Shift takes the priority. Timing is the most crucial aspect of the game.) If dashing, then the somersault is the highest and longest available jump. It'll come useful in some levels. Also, landing on people after jump-crouching will deliver a kick.
Tip: Sliding off upper floors will lessen falling damage; it's also good for ducking.
Punches

Punch is left-mouse button. Here are all punch combos:
Triple punch is one of the most useful combos, because punches are faster than kicks, and harder to be blocked by opponents. Triple Punch is a level 2 move.
Sideways punch is to hit people around you. Of course the best way to fight is to fight 1-on-1, but if you get surrounded and want to punch those all around, press any of the ASDW keys and punch, and you will either elbow the person or just smack him/her upside the head.
Running punches (the difference between sideways punch and a running punch is that there is about 0.3 of a second of running before you're actually running to punch; same with kick).
Crouching punch (Shift + Punch) will punch the opponent in the shins, or in the head if he/she is lying down. Crouching punch + forward (Shift + W + Punch) will trip a standing opponent, but will do nothing to someone lying down. (Don't be crouching near people when they are lying down. They will kick you on their way up.) Rising Fury (release Shift + Punch, level 8) will punch a person twice: once on the way up, and second time (if the person's still standing) on the way down. It's less powerful, and it's interruptible. You also have to wait about half a second before releasing Shift. Also a powerful punch without a name is Shift+Punch, and it will punch (pretty hard, too!) those standing, and bigger opponents who are lying. That's about all for pure punches.
Kicks

Kicks are more powerful, but slower. And there are more of them. Triple kick is blocked most of the time, but it delivers a good deal of damage.
Crescent Moon (Kick, Kick, W + Kick) will knock any person down, and it's powerful, but it's hard to time it correctly, and it's easy for interrupt second or third kick.
Sledgehammer Kick is the Punch, Punch, Kick combination. It's easy to do, slow and therefore easy to block, but works very well against people lying down.
Sideways kicks and Running kicks are almost the same as punches, with the following exception: Jump+Kick will extend your foot until you land, therefore, you can land on people from above using Jump+Kick and still kick them, while you can't do that in a punch.
Devil Spin Kick (release Shift + Kick, level 6) is hard to learn but powerful to use. It will counteract ALL ongoing attacks (but it can be blocked) after the combo is initiated. However, if you are being attacked by lots of people, then they will probable not give you 0.5 seconds that you need to be crouching before you need to release Shift + Kick. It's more powerful that Rising Fury, and can kick certain opponents if they are in the corner and you are right next to them. (Including Muro in the Dream level.)
Crouching Kick is about the same as Crouching Punch; Shift + W + Kick performs a cool backspin kick which is useful mostly against those who are landing on you. But it looks cool!
Shift+Kick is almost the same as Crouching Kick. GOD™ were out of inspiration.
Ducking Kick is hard to learn, but is among the best escape maneuvers. It's A (or D), W + Kick. It ducks and kicks the person in the back of the head.
Weapon Kick is similar to rising fury, only it's accomplished when you are holding a light 2-handed weapon. The move is release Shift + Kick.
And finally, Willow Kick is S, W+Kick. It's hard to block it, and it makes the opponent bend over for about 2 second. Useful, but hard to perform.

Throws/Disarms

Throws/Disarms, as you were instructed, are the most powerful attacks. Yup yup, only you always need to be right next to the opponent to perform them. They're the hardest to discover, too.
Backbreaker. Stand right behind the opponent who is not moving, and press W+Kick at the same time. The kick in the head is pretty powerful, but the breaking of the back is THE most powerful attack of the game. (If you are in Daodan mode, which means you're high on Hypos, then it'll kill most people with one attack.)
Neckbreaker. The same as backbreaker, only use W+Punch. Will deliver a little less damage than backbreaker, but when it's most useful right after a backbreaker when fighting Muro. (Description will follow later.)
Running Throw: run towards the opponent, and when you are right next to him/her, without releasing the running key, press Kick. It looks amazing, but not too powerful.
Running Lauriat: run towards the opponent and press punch. (Level 7.) It's really powerful, it kicks (automatically) the people around the guy you're attacking, and it's really cool.
Tip: to defeat any opponent, stay behind a corner/door, dash into the door (you'll just be running in 1 spot), and right as the person runs inside, running-lauriate him/her. Works every time, against everyone, the one sure way to defeat anyone.
Back throw: stand in front of the person, press W+kick. You lie on your back and throw the person backwards.
Front throw: stand in fron of the person, press W+Punch. You jump over the person, grab his/her neck, and throw him/her forwards.
Fall: run behind a person running away from you, press Punch. It'll grab his legs and fall him/her down.
Regular disarm: stand in front of the person holding a weapon, press W+Punch. Works BEST if you have a force field, and the person is using a Van Der Graff gun. They'll just keep shooting, without kicking/punching you. And you won't be paralyzed if you have the field.
Kicking disarm: stand in front of the person, press W+Kick. Level 14, a powerful kick, looks cool, hard to do.
Armbreaker (the hardest to do): stand behind an person, armed with a 1-handed weapon, press W+Punch. It will break the shoulder, and get you the weapon. It's hard because usually people who have guns are going to face you and shoot you. :-) (Note: if you perform the same with W+Kick, it'll just perform the Backbreaker and drop the weapon to the ground. Also, if the person is wielding a 2-handed weapon, you will perform the Twister instead.)
Twister (which is the same as Armbreaker): stand behind a person wielding a 2-handed weapon, and press W+Punch. It'll spin the person around and give you the weapon. Doesn't look as cool as does Armbreaker, and you will almost never get an opportunity to perform it; but it's still good to know that it's there. :-) When you master them, you will be ready to fight anyone, on the hardest settings. But here are a few tips anyway.

Bosses

The good thing about first 3 bosses (you fight Barabas twice) is that you are 1-on-1. So you don't have to worry about anyone attacking you while you perform super-duper moves.
Barabas

You have to fight him twice, first time in level 3, second--in level 6. He uses a super-duper gun that delivers a considerable amount of damage. Be sure to duck from it. You can use the gun, only you'll not be able to run or jog while wielding it. The second time it's almost useless to shoot him, because he has protective armour. (You'll see it if you actually do shoot him.)
His favourite combos are triple kick (those are so annoying), and Earthquaker (explosive damage, takes away from your field first). There's nothing you can do to prevent Earthquaker (note: if, in level 6, you throw him off the building, he'll fly back up, and automatically land with an Earthquaker), so run away! As far as triple kick, if he start its, after you perfect your timing, you can triple-punch him after first and second kicks, and he won't block it. That, by far, is the most useful attack against him one-on-one. The trouble with him is that if he gets too low on health, he'll start running away from you and rejuvenate. So keep alive and run around while he's healthy, and then triple-punch and somersault on top of him to not let him run away. If you're playing with the Difficult setting, then throws are more useful, because they are a lot harder to block. And be sure to carry Mercury Bow in level 6, because if he starts running way, Mercury Bow will both knock him down so you can jump on him, and deliver a bit of damage. Just run around him the whole time, and you'll get him.

Mukade

He's a lot trickier because of his weapon: when he teleports himself, he lets of a red glowing thingy that delivers weapon damage. It just follows you for a while, so you want to be running all the time. (He is in the end of Rooftops.)
He has a really powerful kick attack (he barely ever punches). You will probably see it when he kicks you about 6 times in a row. The last kick will hurt a whole lot, so beware. Always remember this: your punches are your quickest attack, and once you pop, you can't stop, which means if you get the first punch, then the other too will be successful attacks most of the time.
Weak spot: whenever he relocates, he turns invisible. You can still see him, only you need to turn up game's gamma or your monitor's brightness. When he turns invisible, he launches his red thingy. 30 seconds later, his invisibility will expire, and he will want to relocate. His pattern is as follows: you knock him down, he'll slide backwards and try to escape. If you do a running lauriat (don't be too far way before pressing Punch or else it'll be a running punch and he'll block it), he'll fall, you can kick him, and he'll get up and slide backwards again. You DO have time to run and spin around his neck before he has a chance to teleport himself. If you repeat this a number of times (while he's still visible), you can get him, and he will rarely try to attack you.
Sometimes he will get under the stairs or in the elevator. In those cases, if he doesn't get out, then just reload the game, it's useless to wait for him. (I haven't tried sliding, but the BIG bug of Oni is the z-buffer: you can kill people behind closed doors and walls. They can attack you too. It's funny!) Note this: if you run around him, he will either jump up spinning (and land on you with Electric Kick), or he may crouch. If he crouches, then he'll knock you off your feet, so jump and run away from him, if he jumps, then crouch, because Electric Kick doesn't work if you crouch. Neither does Whirl Kick (I think), Striker Slam, and a whole bunch of other special moves.
But he's possible to kill, so just keep trying and running and doing lauriats.

Muro

You'll have to fight him twice, once in your dream, and once for real. (Note: depending on what you choose in level 13, you can either fight the normal him or the big him. You pick, but the normal him is always funner because you actually fight.) His behaviour is the least like a computer, but still predictable. His worst two attacks are Leg Breaker (don't face him without punching him, or he'll break your leg), and Neck Twister (it's painful, and it only happens if your back is turned towards him). He has this glowing thing when he does attacks, and I think it means that they can't be blocked, but at the same time you can duck. Always duck!
For the Dream level, run around, knock him down, and attack and just be yourself. Try to get yourself as unhurt as possible, 'cause you'll need health (it's a difficult level). Here's my guide for level 14, ending Normal Muro:

There are 2 basic strategies. The first is that you can fight him really quickly, alone, and home to kill him just as quickly (it's possible), and the second is that you can kill everyone else and fight him 1-on-1 in a timely fashion. If you want to do the second, dash forward, and either punch him if he jumps, slide under him, or jump over him. Run to the right and break the girl's back in for first 2 seconds after you load the game file. Run to the left and keep breaking the other girl's back and avoiding Muro. After lots of practice, you can kill the girl on the left, and run to the door from which more of Syndicate troops appear. (The total of incoming people is 3: 2 Rollerballs and 1 Ninja.) Once you've killed her (Griffin's men are too weak to take anyone alone), run towards the exit and lauriat the Rollerball a few times. (Muro will be following you most of the fight, unless you can get Griffin to fight him.) If you can fight Rollerball alone, you're in luck, because by now, having killed lots and lots of them, it's easy. But most of the time you'll have to run away from Muro and punch him every now and then. Here's the most useful move: when breaking the back of the girl on the left, Muro will try to do the Spinny Arms attack. In case you haven't noticed, you are safe from ALL attacks while performing a throw/disarm. Backbreaker takes a long time to do, so if you can time it correctly, after Backbreaker, if Muro is right in front of you, you can perform a Neckbreaker at the same time. It'll be a good attack.
If you're lucky, then you'll still have some force field left around you. The only weapon available is Van Der Graff gun, so if you have a force field, you can have fun and watch them shoot you, come close, and perform Disarming Kick. :-)
If you beat the red Ninja (who's easy to kill), you'll be left 1-on-1 with Muro. By then it's easy, because you can just run around and jump on top of him. And once you're done with him, you're done!
Ending 2: Big Muro. Yes, there are 2 endings (so that you don't freak out), and the second one is less fun. You have the Big Muro. If he's glowing, then he's invulnerable. So what you do is this: run around him, wait for him to perform a special move, and then, when he stops glowing, attack him. Note: don't run too far away from him, because otherwise, he'll just summon you. It's especially bad if you're on the upper portion of the arena and he's on the lower portion of the arena, and he pulls you, and drops you, and you lose a lot of HP. Just run a lot and slide a lot, and duck a lot, and after he does his most favourite move (slide forward with extended hand), you can run up to him and kick him in the butt. (I am serious.) You can't throw him or break his back, just 'cause he's too tall for you. But you can kick him in the butt. :-)

And that's about all! :-)