Gone with V0002, without RTB even, so it want maybe 5 years ago. I hear it left for TBM and died with it.
Although I had a nice one with collectable modules in RTB that could be added or removed from it at will...
And one in retail that can be upgraded by spending points from kills...
But the only good guns are ones that add NEW functionality to the game, such as(at the time when it was released, and though it pains me greatly for every pixel of every character in the following mention) Ephialtes' shotgun.
Here, add some variety to your pile of stuff.