Postal 2, even just the demo itself, is insanely and sadistically fun. I'd spend hours dumping gasoline around and on people to torch them (I'm a major fire freak) If you're wondering how I could play the demo for long periods of time, theres something you can type into console in the demo that removes the 7 minute time limit, although I forget exactly what.
Anyway, the CounterStrike: Source video was very cool, I've grown tired of the same old pre-made death animations (which remain even in the XBox version of CS, and I assume they are in Condition Zero as well). The ragdoll deaths are definitely very cool.