I actually still use a modified version of this physics engine to this day; I wrote it by myself, and it makes me proud. The only part of it I didn't write from scratch was the Pythagorean Theorem (credit goes to Pythagoras, I guess) and a function for finding the angle between two points. It will NEVER, EVER be finished, so stop emailing and PMing me. :D
-=* THE CONTROLS *=-
A and D move left and right.
S ducks; hold it down for a bit and you lie on the ground.
Press S and A or D at the same time to backflip or roll.
E switches which hand you control.
The mouse controls your hand; hold the mouse button to close the hand and let go to open it. You can grab enemies and throw them, or pick up weapons by either end and throw THEM. While you're holding the mouse button down and holding a weapon or enemy, you can press F to lock it to your hand. You can now shoot it if it's a gun, pop the blade out if it's a knife, use the scope if it's a sniper rifle... also you can press E to switch to your other hand. Try picking an enemy up with one hand, then switching hands and punching him. :)
It's not finished, and I'm sorry. I'm working on a two-player split screen Ninja game right now, should be done in a couple months. See you then. :)