Grenade Eggs are a variety of eggs found in Banjo-Tooie.
Drill Sergeant Jamjars will teach Kazooie how to use Grenade Eggs in the Pine Grove of the Isle O' Hags. Grenade Eggs will explode upon impact, and are very useful for defeating many enemies, particularly bosses. They're also useful for blasting open the entrances to many passages. One danger of Grenade Eggs is that their explosions will hurt Banjo and Kazooie if they're too close. Initially, Banjo and Kazooie can hold 25 Grenade Eggs, but a spell from Cheato can double it to 50.