Quake engine is still my favorite. Maxed graphix at 10x 7 - game looks stunning with a - 1.0 LOD w/ Rivatuner. 2 Times AA.
nuttin but gibs!
Also still a big fan of starcraft broodwars.
I wish they would actually remake broodwars with a 3d engine =) that would be heaven.
System Shock 2. Great game!!! awesome ending.
my .02 cents