Now:
Diablo II (the only Online one I consider worth it)
Monster Hunter (when I'm bored, and my buddy feels like playing)
Guild Wars (when I'm really bored)

Formerly:
DAoC
City of Heroes
Final Fantasy XI
...untill I realized that no MMORPG was worth paying money to play. Someday, maybe a game will come out that actually remembers that games are supposed to be fun. Until then, I refuse to play the garbage that is out there now.

DEAD OR ALIVE ULTIMATE LIVE!!! hate me if you want I kick but on that game. I mean I'm not saying i am the best but I damn sure aint the worst.

Ragnarok
Gunz
B n B
DoMo
Grandads Espada
S.U.N (or looking forward.)

I was never really that into online play for quite a while... but eventually I started to play some online games...

Gunbound - was fun and then just got overly boring... and had a bunch of cheating fools...
Puzzle Pirates - left when my wife got bored playing the game since it was the only reason I played was to play games with the wife...
Final Fantasy XI - left for same reasons as Cachecrash...
SOCOM and SOCOM II - was fun for a while but our clan ended up breaking up so it was rather pointless to continue playing online solo...

Currently playing World of Warcraft - am enjoying it... but not taking it so seriously as I did with FFXI... just doing my own thing and teaming up with other players on occasion when we're running the same quests looking for items.

Not really. You have a group of Clonks which you use to build a village, mine for gold and ore and use to make money and to produce other materials. The game has a weather system, so one time it could be raining like hell and your village is flooding. You can choose to abandon it or place pumps to drain the water. Sand storms, cold, acid rain (yes even acid rain), it all happens randomly depending on what settings you picked before you generated the level.
It's a good singleplayer game. The computer is no good but it's fun to have a game on your own. You can play online though, but it's mostly populated by Germans since this game is German of origin (available in many languages). You can co-op to reach a certain goal or just try to kill each other. The settings are different also. Different landscapes are available, but you can also shift the game to the Medival age or Future. There are even cool modes available that allows you to play like a Eskimo and survive in the arctic quite realistically. Well, I can keep bragging along but it's really something to check out yourself.

Screenshots Here

Ultima Online (freeshards), UT 99 and Enemy Territory (<3).
Altho I have far too few time lately to actually enjoy playing the games :/

Oh Ut... I forgot about that. And UT Quake Wars looks great, I hope it gets released soon. (Or it might have been already released if I haven't been updating the news >.>)

I played a few mmo's like FFXI and SWG for a month and then quit, but the games I have played online seriously are:

-UT99
-Anarchy Online
-Asheron's Call 2 (I would probably have played this for another year if there was actually a player-base, but only a couple hundred people played this. :/ )
-WoW

I am absolutely shocked that no one has mentioned Graal Online yet. I played that for four to five years (started in Oct of 1999 (or was it 1998?) and played until May of 2002 (or was it 2001) when it went totally p2p). It was fun and I had a lot of good times, even with them basically going back on their word and making it p2p.

Ahhg! I was going to mention this! I started playing Graal soon after it changed from Zelda Online, so I was pretty old school as far as it was concerned. The player base was hilarious and while the game itself was broken beyond belief (How many items did you get screwed over thanks to archaic quests not working anymore?) it was still a lot of fun.

Ragnarok Online, for about 5 months or so (when the game was free). Looking back, I don't even know why I stuck with it for so long ... lag was terrible, cheating was rampant, no account was safe from hackers, and the amount of BS was amazing. The game probably improved a lot when it went P2P, but I was so sick of it by then, that I never tried a paid server.

I play WoW occasionally now, when my sister isn't playing.

Gunbound... Shame on me.

Oh yes and Enemy Territory is so addictive.. never start playing it kids!

Enemy Territory anyone? >.>