Death island and the ice maps Gulch is good too but i suppose its dependent whether or not its team slayer or ctf?

for snipers I would have to say timberland (slow games but usually go high K/D) or Hang em' High (always loved this map design)

for CTF (with rockets) rat race (hardcore matches with fast pace gameplay, usually get some flag captures)

for CTF (with usual settings) Ice fields (usually pretty hard to get flag captures, if your team is good you get lots though)

~My Favorite Maps For CTF~

Blood Gultch (Normal Shields. Normal Weapons. Warthogs Only).
Beaver Creek (No Shields. Shotguns Only. No vehicles).
Boarding Action (No shields. Normal Weapons. No vehicles).

~My Favorite Maps For Oddball~
Boarding Action (Normal Shields. Normal Weapons. No vehicles).
Wizard (No Shields. Normal Weapons. No vehicles).

~My Favorite Maps For 'One Shot'~
Wizard ('One Shot' normal settings).

~My Favorite Maps For Zombies~
Wizard.
Damnation.

~My Favorite Maps For General-Killing~
Hang 'Em High (CTF-Red-Team, Normal Shields, Snipers, No Vehicles).