Vampire: the Requiem (solves some of the logical flaws in the earlier Vampire: the Masquerade)
GURPS
D&D v3.5
For a simple evening's gaming, with nothing in mind but hack-n-slash and the joys of backstabbing for fun and profit, Paranoia! (You're all Troubleshooters, working for the Computer that runs Alpha Complex. The Computer is insane. Anyone pointing this out is a traitor, and subject to summary execution. Mutants and members of secret societies are traitors. Every character is a mutant, and belongs to a secret society. You have six clones. You may have to carry out your missions with experimental equipment from the R&D department, which runs through clones like a cargobot runs through batteries. The equipment usually works about as well as you'd expect, in an underground city run by an insane computer. Often, it doesn't even explode - for more than a few dice of damage! Rejecting this equipment, of course, is treason. Have fun...)
For CRPGs, I'd have to go with Grand Theft Auto: San Andreas (it counts because you can increase certain abilities, based on how often you use them, so that each iteration of Carl "C. J." Johnson is unique), The Bard's Tale, and Champions of Norrath (although I haven't been able to play that one since my PS2 went to The Great Hardware Depository In the Sky).
_________________
Sodium is a metal that reacts explosively when exposed to water. Chlorine is a gas that'll kill you dead in moments. Together they make my fries taste good.