Fragmentation Grenade
From Halopedia, the Halo wiki
Summary
The UNSC M9 HE-DP (High Explosive-Dual Purpose) grenade is a thrown fragmentation device. Use it to suppress or disable vehicles, except tanks. It can be thrown, rolled, bounced or ricocheted into places direct fire weapons can't reach. Increase the angle of the throw to toss it farther, or to get it over obstacles. Be careful not to throw it too close to your own location.
Note: In the most recent update of Halo 2 on Live the Frag Grenade's fuse has been shortened, but it is now more powerful.
There are many Frag techniques available to you that can mean victory or defeat. By using its bouncing, the terrain around you, and the enemy itself, you can severely damage your oponent and give you the upper hand in the battle.
It isn't the most useful weapon against an Elite, but it is excellent to get rid of a group of Grunts.
