Blinded sights on guns
Huh!! Never tought of that.
I was trying to think of alternate methods to anno...er...confront people. Mud to block sights, tar to lock a weapon in place, foam to jam the barrels, etc. I had this thought of a squid sneaking up behind people and making them unable to fight back for a small period of time. It wouldn't win DM's by yourself, but in point games it could prevent the death of your ally-on-the-spot.
I'm sure more creative people could come up with others. I've been trying to come up with one that would simply unseat the enemy gunner, like when a gun is fully damaged or far too hot. Force them to sit back down and re-aim. I can't think of anything interesting enough. Same with the "force their gun to go into reload mode" ammo.