Ill have to say Global Ops, Both IGN and Gamespot state that if CS hadn't come out first, this would be peoples CS. if you started playing CS first, you prob won't like it, apparently its to hard for the CS'ers.
Graphically its not the best but as far as team play goes its the shiznit. If you haven't played it, you can pick it up for about 15 bucks now and still plenty of games going on gamespy all day long.
O and one more for anything made by Blizzard, but thats kind of obvious