How is there no poll?
By far MW2. Online I used OMA all the time (but I never used the grenade launcher) you wouldn't won't me on the other team in SnD, espicially when I was on defense
I would put a claymore with a c4 in front of it, and do that in 2 different places to guard a bomb, then guard the third way in, or go over to the other bomb.
The obvious issue with MW2 was noobtubes, and rpg's
One fun thing that works in MW1, world at war, and MW2 in SnD is this cheat: If you are playing with one other person then go into private chat. If one of you dies then that person immediatly presses start, you will be looking at the enemies uav (on about a 5 second delay) and for example you could tell your friend if he has the bomb that no one is at bomb site b, go plant. (well it worked in every mode, but unless there was a sniper or someone using a helicopter or AC130 there is no point besides for SnD, did stop some nukes this way though)
One time I was doing this and the guy with the bomb was killed by my claymore, so I set up my claymores and c4 and the friend I was playing with came over to guard the area with me, and it was down to 2v2 from the start. Suddenly we couldn't move, our screens were practically frozen. Then there was a big explosion... double kill. Someone on the other team used a lag switch and I still won it for us.
But yeah after MW2 they sucked, even if I could I am not buying anymore
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Well you can go with that if you want.