Wolfenstein (2009). I shot a guy in the throat and he started spewing blood and choking on it. Pretty much every gun can shoot limbs off people, or Left 4 Dead 2. If you cut them in half, their intestines spill out, and there's blood EVERYWHERE.
OR EVEN
Saints Row 2 for the mere fact that you can chainsaw random innocent civilians. There's no gore, but still.
OR MAYBE
The Darkness. The entire end sequence is a huge slaughter fest.
Dead Space ft--Oh wait, that's the most disgusting game I know.
Wuss.