Just in case thewasn't quite violent enough for you, the latest version of has now been released. It ups the gore quota fairly significantly.
In development since 2010, the mod adds unique gibs, death animations, dismemberments, headshots, executions, plus a number of visual upgrades that put a bit of extra sheen on the venerable shooter's graphics.
Essentially, by installing the mod you'll get a much more physical version of the game, which gives you the ability to really mess with enemies and the environment. You can, for example, kick demons in the face, push explosive barrels around to set up traps, liberally sprinkle the entire level with blood and guts, and even “perform cinematic executions and RIP AND TEAR your foes with your bare hands.”
So if you've ever thought the only thing that was missing from Doom was the ability to tear an enemy's head right off, then fling it into another poor demon's face, Brutal Doom might be just right for you. In all seriousness, there's some really clever work on display here, some of which you can glimpse in the splatterfest trailer above.
To play, you'll need a functioning copy of Doom or Doom 2. There's a handy guide for getting it to work