Ok so i was using a heavy so i had the gattling gun and an AR as my default weapons, then when i switched to light body and went into a game i was running around super fast wielidng a gattling gun(it was actually really awesome but it definately needs to be fixed to prevent people exploiting it). Anybody else experienced this glitch?

No, not yet, but I have noticed some other issues that are along the lines of what happened to you. Long story short, I created a character,
customized him, played with him, and noticed his voice wasn't what I picked so I deleted him. So I chose to progress one of my other
characters via some online freeplay and low and behold the character I just deleted, who was no longer on my system or in the memory,
suddenly showed up in the opening cutscene. He was very diverse so I know it was him.

Also, when you play with one character and then switch to another and play with that one you (sometimes) will still hear the previous
character's voice when reloading, supplying a friendly, or taking an objective. It is a buggy mess.

Thanks for confirming. I was on the verge of finding this out myself today. I was wondering to myself after I switched my armor from heavy to light on why it told me that I had a primary weapon selected already even though I haven't selected a weapon for my light weight.

This glitch also brings with it something far more nasty..

When having the heavy weapon equipped as someone who can't wield it, you'll become invisible to most players.

on the side subject of the minigun - i was a heavy using it (cry more!) and sometimes when i would use the left mouse button it would just spin the barrel as if i was using the right mouse button - i think i fixed it by quickly using the right mouse button for a second then switching back to the left

"Heavy" build: heavy body, soldier class, armor piercing rounds, kevlar, scavenge, minigun/shotgun "Baloni A-HAHAHA"
get more minigun ammo from the guys you killed with the minigun >_O

I tried to replicate this on multiple characters but to no avail, I'm guessing it's just some random glitch... probably happens because brink's code is more unstable than a crack[censored] lol