Gordon Freeman

Barney stepped out with a satchel, and pulled some dubious-looking electronic equipment out. "Oh, before I forget: each team gets a radio to coordinate with other teams and personnel to make sure we're smooth. The channels are secure, and should be able to reach any team member within the City 17 area. Remember: this is your lifeline--I only have one to give you. Look at the channels on the side; they're labeled so you can tell who's who. Good luck, everyone!"

The channels are labeled as follows:
Channel 1: Destroy
Channel 2: Dunkirk
Channel 3: Ninja
Channel 4: Tennyson
Channel 5: Direct to Valerie/Medics
Channel 6: Global