Could be included:

All Your Base CTF (Good for 2v2s, not too damn popular but some like it)
Marshland of Evil (A somewhat standard include in mappools, good for any amount of players)
Space Island Level With Islands (Fitting for any amount of players, and quite popular)
Toxin Twister (Some seem to like it and it's definately a good level)
Unconventional Coffee (Dammed good level for team-games)

Unnecessary:

Quasar Quandary (Many consider this annoying, it is rather campy... Takes long)
Whantil (Dammed big level, doesn't really suit 2v2s)

Note: this just an opinion, rather ignore it than throw childish insults.