There is also .44 SMG, Tommy Gun. It's pretty fun with explosive ammo, basically a full auto grenade launcher.
I've added the Tommy Gun to the weapon list on the wiki:
http://www.underrail.com/wiki/index.php?title=Tommy_GunWith explosive ammo it's very strong indeed but the hefty precision penalty is something to worry about. However I'm planing to give it a go with a hybrid build which is supposed balance it out with a pretty reliable stun from the Combo feat:
Other weapon of choice next to the Tommy Gun is one of the two unarmed uniques, Ripper's Glove or the Claw. Either of them hits for 4AP @ 14 dexterity so ideally 3 consecutive hits (12 AP total) will guarantee a stun. A stunned opponent has his dodge/evade skill negated which leaves him extremly vurnable to burst fire from the Tommy Gun. I'm pretty sure that this will be enough to counter the precision penalty and the low perception because not only the enemy can't evade now, I'm basically firing point blank. With explosive ammo a little bit of a distance is advisable though.
14 dexterity also fits perfectly for the Tommy Gun to bring the base AP from 15 down to 9 which allows for 18 AP bursts. With my 50 AP pool I can hit 3 times with the glove for 12 AP and burst 2 times with the Tommy Gun for 36 AP plus a third time if Commando kicks in. The Tommy Gun has a 50 round drum magazine and each burst is 7 bullets, so reloading will only be neccessary after 7 bursts which is insanely good compared to the rest of the usual SMGs.
One other advantage of this build is the very strong synergy between the debuffs slapped on the enemy. Wrestling and Suppressive Fire penalizes their AP, MP, and hitchance, while Vile Weaponry, Expose Weakness, Bone Breaker and Opportunist stack up for some insane damage, overcoming the biggest downside of SMGs - low damage against high mechanical resistance/threshold.
Naturally a melee/ranged hybrid will be very hungry for skill points but I still manged to fit everything in I need, even stealth and crafting. Since my main weapons are uniques I only have to worry about crafting the armor, the explosive ammo and the electronic gear. Plenty of points left with 5 int (7 with Junkyard Surprise). Some points can be eventually shed off from stealth if needed for crafting:
http://underrail.info.tm/?build=AwGloJgVhB2ECMAWEA2EN0GYOKzcPGBfIkADhVlC3UIWFAdCSbcI7C53XgXJAQEILBBECoMKPCgBONOlTxYOWLKAI would love to squeeze Nimble into the build but all the other feats are crucial. As I mentioned before the Wresting/Suppressive Fire help alot here. I play on hard permadeath style so I need every point in endurance I can get but if someone doesn't mind playing a glass cannon, which is fine on normal difficulty, it's a viable option instead of constitution to increase perpection on levels 20 and 24.