Halo 3 Beta Video Strategy Guide

The new Proximity Mine is found on Valhalla, atop the bases next to the two Brute Spikers. The mines are especially deadly against vehicles, since they're usually moving too fast to avoid them. On foot, you'll hear the mine beeping well before you step on it, though in the heat of battle you might miss the cue. Mines can be detonated remotely by shooting them, which can serve both offensive and defensive purposes.

You can also use mines to guard your backside. Toss one at one end of a cave, then snipe freely from the other side. When you hear the boom behind you, it's time to pull your head out of the scope and turn around.