PA-15 – ★★★★★ Handgun
Calico and Thunder's lovechild. Also kinda slutty because French. Boasts a weird AoE attack that, amazingly, stuns stuff. The stun is better if there's multiple targets in the AoE, but worse vs. a single target. The damage isn't great (6x multiplier + not super high FP) but you mostly want the stun and the damage is a bonus.
Note that the stun's effective area is actually not as wide as a normal stun grenade because it's a narrow vertical strip rather than a normal radius. Also, it won't stun anything a regular flashbang won't already stun.