So far, I have played through the Campaign mode twice and I have come across several weapons glitches. Below is a list and description of what happens.
Mini Gun Glitch: During "Survive the aerial assault" in Act 1-2 "Last Train From Explosion Town" I used the Mini Gun on the vultures until the battery depleted. Somehow the battery in the same gun reset, and I was able to pick it up again, but it also had an infinite battery pack.
Weapons Confusion: Occasionally, switching between the left and right weapons, Gray will hold the new weapons as if he was still holding the old one. For example, in "Worst Family Fun Vacation Ever" I switched from the Boneduster to the Screamer, and Gray was holding the Screamer as if he was holding the Boneduster.
I will have more as I come across them. I will do my best to get pictures or video, but as of right now, I have no way to record from the PS3.