After playing a gain I think I got them all but correct me if I'm wrong:
Pistol: Does something on enemy kill.
F: Explode, I: Slow field, L: Lightning Bolt, M: Purple speed boost pickup
Rifle: Delayed effect when reloading with low/no ammo
Neutral: Damage stuff nearby, F: Damage stuff + explode, I: Slow things nearby, L: Lightning strike that chains, M: Gives player speed boost
And then there is a fire explode barrel and a lightning strike barrel