Infiltration Compass - This mutator has a little direction display in the bottom. Basically it tells you if you're heading N, NE, E, SE, S, SW, W, NW and I can see this being use to coordinate attacks.
http://dl.fileplanet.com/dl/dl.asp?planetunreal/realmaps/mutators/infcompass.zip
http://dl.fileplanet.com/dl/dl.asp?planetunreal/realmaps/mutators/infcompass.zip