I could write lots and lots of words about the super-cool, super-violent new PC game Hotline Miami. In fact, I've already kinda done that.
The game is: Awesome. You should: Play it. But if you're still unsure what it's all about, check out this playthrough of the first level, uploaded by JereHakala. This guy/gal is waaaay better at the game than I am, but that makes it pretty fun to watch just how quickly and crazily a level can go down.
Also, go listen to the whole soundtrack, because it is killer.