I had the same exact thing. Its like... Cobolt Volcano sometin. I sold it though and found an automatic one thats way better.
The most ridiculous gun? Boy do I have a few for you guys... Shotgun that shoots bullets (duh), those bullets impact in the formation of Smiley Faces. Rocket Launcher that shoots rockets that divide into rockets until it hits something. the most I've gotten it up to was 21 rockets. SMG that shoots bullets that spiral and bounce off the ground (awesome for fighting the ants.) Revolver that shoots magic bullets that weave side to side, and bounce off one surface. (get this off a named for a quest.) I have many more but I'll stop here. Also, the gun that shoots the wavey bouncing blue bullets, is T.K.'s Wave, you get it for getting his leg back from Scar.
Most Eridian weapons suck sadly I can't find a use for them unless the target is slow and stands still a lot... Other than eating shields, it really doesn't do damage to health.
You didn't know about the GearBuilder? xD It's all based on the different manufacturing companies in the game, Hyperion, S&S, Atlas, etc. Different manufacturers have different trademarks and use different materials, so the gearbuilder bases a lot of looks and stats on whatever manufacturer it chooses.
No its hard not to know about different manufacturers I just had no idea there was 17,750,000 different weapon variations.