Oh, it's an energy mace/melee weapon, not a net thrower. That's pretty neat as well, especially as it looks like it's clashing with the lightsaber without getting bisected in return. That handle seems quite odd however; it looks like a tonfa, but with an end that could mess the user up more when being spun. Zeppo (and other mace wielders) must have some pretty strong grip strength to not hit themselves when swinging at opponents. I'm also not sure about a stun setting working that well versus a lightsaber. Maybe against someone who's a Jedi Knight (or at least Force sensitive) who can use a lightsaber properly the mace would get destroyed, but Finn needs to focus on not chopping himself up first.

The energy mace is definitely a stun weapon though. Stormtroopers were pretty well known for being weak-willed and poor at shooting (whether or not it's actually true), but even they wouldn't be stupid enough to 1v1 melee with a former trooper if that former trooper is wanted dead. I guess the First Order contacts passed the info to the troopers (and Kylo Ren) coming in that Finn had ditched their ride. I could see Kylo possibly wanting Finn back to implant some mind control triggers before sending him back to the Resistance because Poe disappeared from everyone's radar. Poe only had "you will be a double agent for me"; Finn might end up with something even more specific.