1. Call of Duty: Modern Warfare (the entire series) - Can't stand it. I played the original, and the multiplayer was generic shooter that had experience to suck people in, and the single player was a long hallway that led to a white dot, and when you get there, the hallway turned a different direction and you kept going, shooting people all the while. Boring game. I returned it within two weeks of buying it.
2. Halo - See criticisms above. The first game was a very good game and undoubtedly the best early Xbox title. Everything beyond that was your typical shooter stuff with a story that just screamed "lol we have no ideas let's just see how much BS they'll buy".
3. Grand Theft Auto - I do not see the appeal of driving around a city doing criminal things. I guess a lot of people have some deep dark desire to actually do these things and GTA provides them a legal, risk free way to experience that? Yeah, no desire to do any of that stuff here, so the game is just not interesting for me.
HOWEVER - I do like shooters and freeform games. Fallout, Oblivion, Metroid Prime, Half-Life 2, Team Fortress 2, L.A. Noire - all of these are excellent games. I am not anti-shooter; I simply dislike the two most popular ones.