With so few good new titles being released these days, especially by major studios, I figured I'd make a thread for everyone to share your favourite classic or older games, especially if they're lesser-known titles that others might have missed at the time.
I'll open with The Saboteur (2009), Mercenaries (2005) and Saints Row 2 ( The 2008 original)
Eternal Darkness: Sanity's Requiem for GameCube
X-Men Legends and X-Men Legends 2: Age of Apocalypse
Marvel Ultimate Alliance
GoldenEye (duh)
Diablo 1 & 2
EDIT - Forgot to add:
Shining Force 1+2 on Genesis
The Ooze on Genesis (pretty unforgiving)
Geist on GameCube (janky but fun and fairly unique)