Has to be Hardpoint for me, closely followed by Bounty. Love the objective nature of Hardpoint but puts Headquarters to shame as it has a good rotation around the map rather than feeling like one team always stomping the game in HQ. Something so exciting when you get a decent game and a little bit of comms between FGers and we can work our way out of sticky situations.
Bounty shows that the subtle change to a gamemode like TDM can make it hugely popular and fun. The objective pulls you in as you can see where the Bounty is at all times, plus it gives other members a role of either attacking or defending given the fact you can get 5 points for a bounty kill. Wish they kept Bounty kills on the stattracker though, I feel like that would help show how much of a MVP you are in the round.
I used to love Search and Destroy on every previous CoD but now I can see why only having one life can be quite frustrating. Early on in this MW2 game, we were loving Cyber Attack due to the unlimited revives you can have. However, the others just flow better as everyone is active all of the time.