Unreal Tournament 3, purely so I can nab some of the achievements. Literally NO-ONE plays multiplayer on that game. I tried for about an hour to get a game, no luck at all. It'd give me no matches every time I tried to search for a random match for about 5 tries, then it'd bring me into a lobby with this one guy who booted me from it as soon as I entered every time. And his was the only game matchmaking would find. He was confusing and extremely annoying at the same time.
Also, maybe Alien VS Predator. It's not necessarily dead, but it's not exactly bustling. Few things are funnier than getting to play an Alien in species wars against people that are stuck as playing as Marines, running up behind them and impaling them every time they respawn. No-one would willingly play Marines, they can't kill anything.
(Unless it's an Alien that's in front of them, but only an idiot would run in front of anyone as an Alien)