Arica Harbour: Bad Company 2.
Laguna Presa: Bad Company 2.
Nelson Bay: Bad Company 2.
Panama Canal: Bad Company 2.
Isla Innocentes: Bad Company 2.
All for different reasons, and all in Squad Deathmatch, mainly because I've grown tired of Rush and I hate Conquest.
Arica Harbour: Emphasis on close quarters, urban warfare makes for hectic battles with a lot of hasty, split second choices to be made when it comes down to confrontation. Cover is bloody everywhere at the start of the match and you can use and abuse it to your advantage, but towards the end, you have to learn to adapt as walls and buildings come down around you, where you might just favour a more mid range weapon.
Laguna Presa: The recon's (Real recon, not the bastards that sit at the back of the map taking pot shots) wet dream, give a good recon player motion mines, a VSS or a shotgun and he'll absolutely wreak havoc as the ghillie suit makes for the perfect camoflague to ambush unwitting targets as they walk past. Staying on constant alert and moving from cover to cover, restocking your ammo with fallen assault kits and you'll come out with at least 20 kills.
Nelson Bay: Night time, foliage, large areas and a building that 90% of the conflict will take place in as "snipers" try to reach the top for the area with the most view over the battlefield, but also the area that's most vulnerable to attack, you'll spend most of your time fighting over a 3 to 4 room building in incredibly cramped quarters, so a solid CQB weapon like a shotgun, the AUG or the VSS is gonna be your best friend, and it makes for some really frantic and fun as hell battles.
Panama Canal: A similar set up to Nelson Bay with a massive building where 90% of the conflict will take place in with a couple of difference. Day time and wide, open killing fields with a fairly easily defensible position right at the top if you have a reliable squad, it's almost King of the Hill in Squad Deathmatch form as people vie for control of the top floor of the building.
Isla Innocentes: Forests, trees, a small village, a tank and a lot of places you can hide in off the sides of the map to ambush people. If it weren't for Arica and Laguna this would be urban guerilla warfare at its absolute finest with people popping out of buildings, off the side of ledges and cliffs, out of bushes and out the back of skips just to pop shots at you.
In short, BFBC2 has some of the best, most frantic, hectic, fun and most well designed maps I have ever seen in a first person shooter.