I can't seem to find a list of the available experimental grenades and ammo types that can be developed in the Proving Grounds facility, as well as their effects.
There are 5 types of Experimental Ammo, and 3 types of Experimental grenades.
As a side note, Ammo applies to Sharpshooter pistol shots.
- Armor Piercing - Bypasses an enemy's armor. No bonuses against enemies without armor.
- Dragon Rounds - Passive bonus damage and a chance to light targets on fire. (Enemies immune to fire can't be lit on fire, but still take the bonus damage)
- Talon Rounds - Reaper Rounds' big brother! +20% passive crit, and an extra +1 damage on critical hits. No extra range penalties like its predecessor.
- Tracer Rounds - +10 Aim while equipped.
- Venom Rounds - Passive bonus damage and a chance to poison the target. (Enemies immune to poison, like Chyrssalids, still take the bonus damage)
- Acid Grenade / Bomb - Shreds more armor than a frag grenade, applies Acid to those hit, and leaves acid terrain tiles on the map for a few turns.
- Gas Grenade / Bomb - Larger area grenade that deals damage and poisons enemies hit.
- Incendiary Grenade / Bomb - High damage and sets enemies on fire.
And, though you didn't ask for it, why not --
Heavy weapons are tiered. The "Heavy Weapons" become available once you unlock the E.X.O. suit, and the "Powered Weapons" become available once you unlok the W.A.R. suit.
- Rocket Launcher - Unlocked by default. Deals explosion damage in an area & shreds armor.
- Flamethrower - Cone of flame to deal damage and ignite enemies.
- Shredder Gun - Cone of bullets to shred armor and cover.
- Blaster Launcher - Powered Weapon. Upgraded Rocket Launcher.
- Hellfire Projector - Powered Weapon. Upgraded Flamethrower.
- Shredstorm Cannon - Powered Weapon. Upgraded Shredder Gun.
- Plasma Blaster - Powerd Weapon. Linear area damage.
Here's an imgur album assembled by SYLOH with the in-game descriptions.