Spooky
A nicely done outdoor canyon. Frenetic at first, because of the baddies waiting for you, but once they're gone, it's quiet again...There's a fast-moving river through the middle, with access to an underground cave, and plenty of nooks and crannies. A single manmade room overlooks the field, with teleporters to various high points. Probably needs three minimum to obtain decent carnage rates.
Levels in map "Spooky":
Spooky