Bomb Planted Medal
From Halopedia, the Halo wiki
The Bomb Planted Medal is a Halo 2, Halo 3 and Halo: Reach medal, awarded for planting a bomb in the opponent's base. It is available in all multi-player Assault gametypes and has a Bungie difficulty rating of 6 (out of 10). It is represented by a red inverted triangle with a lighted bomb.