My favorite was and still is CS desert.
Reason why: Objectives were easy to get to (even with vehicles) and the battles for TC and comms were fun and heavy when a good amount of players are on and the battles you were able to have were awesome and most player feel "USEFUL" or at least more then they do now.
Comms: Comms had a good and i mean A GOOD CQC combat about it when breaching or defending as it was all random if afghan would rush, nade, and even snipe into comms. afghan also would snipe and try to weaken US forces before we even got close to the objective.
TC (Toxic crater): It was hell on CS desert and we loved it, either US or Afghan got there first (mostly US) and the other would either snipe, RPG, and even full on RUSH the objective and it gave lots of fun not only that but the hills provided much cover and more attack approaches to any objective.
Bases: Could be upgraded now but were fun regardless. The only one in need of such a make over would be tali base (RU base) for lots of reasons.
UK OP: This OP was not a OBJ but a point over looking TC and was useful for callouts for flanking and sniping of TC and thus you can imagine the amount of battles that happened for this point as one who holds UK OP has full power to do lots of what they wanted to TC.