Softens people up before they enter. Enemies can bounce grens off wall and easily kill it. At the split, the corner of the room on the right, facing the elevator. Tears People up quickly. At the top of the ramps.
Most people come through there.
Nobody puts one here, ever. Elevator hole protects it from bouncing grenades nearby. Unless it's a level 3, most classes can make it by. Opposite the flag, in the corner. My favorite spot.