DOOM: Favorite would have to be E4M8: Unto the Cruel. Knowing it's the Final Level, it pumps me up, and I Kill everything in my sight.
DOOM 2: Map 30. Icon of Sin. Fun to just see how long you can survive on Ultra-Violence. Record is 3:15. Longest I ever went without getting Tele-fragged.
Final DOOM: Never played this game, but Go 2 It looks like a lot of fun.
Makes sense if you don't think about it.