This is what they should be:
He grenade: Poisions zombies in the sector (- 2 health for 20 seconds or somthing)
Flashbang: As said, blinds the zombies, thus turning the players screen all white.
Smoke Grenade: If zombies go in the smoke, the players screen will partially have some smoke on it, obstructing the players view
This is imo I think they should be. Anyways would be fun seeing new weapons.