WARNING: Do Not Download Toribash

If you acquire Toribash, there is a very good chance that you will lose sleep. You have been warned.
At heart, Toribash is a turn-based physics-intensive ragdoll simulator, which might not sound too interesting until you realize that you’ve been given the keys to a whole series of devastating fighting game moves that put Mortal Kombat fatalities to shame. Think “multi-player Stair Dismount or Truck Dismount” and you’ll have a pretty good notion of where this is all headed.
The Toribash site itself has several tutorial videos as well as an official trailer, so head over there and check them out. Then, if you decide to download the demo, hit the forums to learn some seriously devastating combos. You only get access to the single player sandbox portion of the game with the demo, but it’s enough to get a taste for it.
Just don’t blame me when you look up, bleary-eyed, from your screen and realize that several hours have passed since you downloaded the stinkin’ thing.