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I know it's sad but it'll keep me happy during the cold and wet months ahead :)
Free month trail download (450mb)...damn addictive though...
UT 2003 should fulfill your need for carnage, but the system specs are a little high.
SOF 2 is definitely carnage-laden, but it gets a bit boring, if you can believe it.
Battlefield 1942 is mostly multiplayer, but the single player option is fun. You can tweak the settings to provide more of a challenge. Graphics aren't top notch, but it's still fun.
That's off the top of my head, and they're all FPSs. If you want RPGs, let me know. I have some suggestions from fellow gamers on those since I'm not a big fan.