Grenades that I personally, and maybe share the wishes of other, that 343 might add.
Frag Grenade- Large Blast radius, Light Damage.
Really a crowd control weapon. Not too powerful, but does enough damage to pop ones shields, or kill a badly damaged unit.
Plasma Grenade- Small Blast radius, Heavy Damage, instant death if stuck.
Does the real damage, as being even near its center means death, and even worse if one is stuck
Spike Grenade- Medium blast radius, moderate damage, instant death if stuck. Massive damage to vehicles.
Does decent damage, more for sticking opponents and does exceptional damage to vehicles.
Firebomb- produces a swathe of flames around the targeted area, will kill if struck by grenade.
More of a means to control invisible units and do damage over time effects
Smoke Bomb- Wide radius No damage, creates a cloud of impermeable smoke that effectively grants cover for anyone not wanting to be seen.
Bubble Shield Grenade- upon impact to any surface, this device will create an impenetrable barrier, rending all that lies within its protective surface from harm. Cannot be passed through, nor can anything thats within escape.
Perfect defensive and offensive weapon. An example is that you can either bar the paths of enemies, ensnare an opponent within to keep from escaping, or defend oneself from heavy fire.