I'll post a couple of my custom DukeMaps. Also, I have several that were authored by a good friend of mine who used to be a UO slut. We'd get in dire trouble at work for running Duke at lunch and in the evenings (err, will waaay late at night). But our maps were always customized for absolute maximum DukeMatchiness.
But TF2 is pretty darn fun, but I noticed that my system needs an upgrade since it's a bit framey for me. Pound for pound, I've still enjoyed the original Unreal Tournament more than all of them combined (first person shooter that is) Nothing like going Godlike when you can here the whimpering of all your LAN-friends. Luscious.
My favorite of all times still is Descent 2. (also owns the best soundtrack of ANY game now or then).