Oh god, my favorite moment in Manhunt was going through the junkyard and passing by the trailer. There was a guy sitting on the crapper, which was poorly positioned right by a window. So I picked up a nearby brick and chucked it through the window, braining the guy before he knew what was going on.
I don't know if it was a fluke or something, but it was one of my most memorable gaming moments from my teen years.
I tend to get excessively violent with my end-game wizards in Oblivion. Nothing beats walking into an inn and casting an AOE mass death-by-fire/shock spell, then piling the bodies up in the middle of the room. Argo the Wizard was a bad, bad man.
Also he wore flaming pants when I got bored. Good for training restoration, what with the constant low damage being dealt.
Horse Crack was another great spell I saw a friend make. It boosted speed on touch by a crapton, and he'd use it on his horse and speed around like he was in a sports car. Not violent or anything, but worth mentioning.
WH40K: Space Marine is good if you like pulverizing Greenskins and getting covered in blood. And then there's Red Dead. Gut shots are pretty nasty, what with the person trying to crawl off before bleeding out. Going around turning places into ghost towns is always fun. Finally (for now), I present Way of the Samurai 3 (only one I've played). Playing on realistic (I think that's what it's called) and using a long blade with Draw Stance is godly. If you piss off a group and do their redemption missions you have to fight 100 dudes, and that can get pretty awesome. Maybe not as violent as you're wanting, but you can juggle back and forth between factions to keep putting yourself into them big battles.