from videos and streams I've watched I've seen shotgun bullet revolvers that melt dudes, auto shotties that are accurate at range (small spread) and have scopes and do fire damage, pump action rifles with revolver reload and iron sights that do explosive damage, a rocket launcher that shoots 3 acid rockets at once, etc.
I've also seen a few weapons that were identical in everything but reload speed, accuracy, and damage.
It just depends on how the generator's feeling at the moment. There are some wild variations, but the procedural generator isn't the messiah of random game loot generation like a lot of people want to make it out to be.
Though I love the way the grenade mods work. I saw a grenade mod called "Transfusion" that explodes, homes in on a target, leeches health and then gives it to you. My favorite is the "Longbow" mod....teleporting grenades.