Easy Question For Halo 3 Players?

Hi, I was watching a video of Halo 3 matchmaking and I am pretty new to Halo 3... I noticed that when he was driving a Warthog and he had a turret he would get a medal every time his turret got a kill. What exactly is that medal and how good is it? I think its a good idea because in Halo 2 (which I play online) nobody wants to drive the Warthog because they dont get any credit.