Imagine a weapon that bounces slightly less than a normal one would, that has the ability to stress players out tremendously pending where it impacts. Grenade does just that. It will bounce four times, losing inertia with each one, then explode furiously at fifth contact with the ground. If you're near it, you might not be playing much longer. Best used when an enemy is down in a pit.
Tri-Nade takes something simple, then makes it complex. Matter of fact, it defies all logic. That's what makes it great! Tri-Nade bounces and acts just like Grenade, but then upon explosion, releases three smaller projectiles that deal 25HP damage a piece (including the original explosion.) This all culminates in a real bad time for the opposition.
If you thought Tri-Nade was a work of art, feast your eyes on Multi-Nade. Two more projectiles fly out of this bad boy, dealing 20HP damage a piece. What more is there to say?
Grenade Storm is an air-strike weapon that is probably more on the "weird" side than it is the "unique" side. Fifteen projectiles fall from the sky, with fourteen dealing 8HP damage a piece, while the giant grenade you aren't expecting at first deals 50HP damage.