The OFPS I had the most fun with were Duke Nukem 3D and Call of Duty 1. I still do, sometimes.
I do have BF2, but I don't like the communities around OFPSses. I don't like being bossed around by angry French pre-teens. People who write words with numb3rs. People who whine if you pull off a handsome shot. People breathing down microphones. People pressing the confirmation button endlessly so the only thing coming out of the speakers is "Yes sir!" a thousand times. Being kicked if you don't respond on certain comments. Being kicked if you respond to certain comments somewhat less then politely. I almost always quit a game, grumbling "kids...". Maybe I have a bad track record picking servers.
I'm tempted to try TF2, but as that seems to focus on teamplay very much I doubt I'll like it. I also hope Battlefield Heroes turns out great, but reading the comments people make on the BF:Heroes site, that community will consist entirely out of angry pre-teens, but from around the globe.