My one and only as of late. I used to run with a Pulse Machine Gun, but with some testing I'm hoping this can work as well. It's got hell of a less drain than the Pulse Machine Gun, and I have two variants, one for Accuracy, and another for Power.
The Accuracy one seems more viable for online combat, as it's got a faster Muzzle Velocity, but it's range is shorter by 2 points. S'not much, but hey.
Also, if I manage a steady bead it greatly outshines the damage that the PMG does, at less than half the EN cost too. That's if I get the jump on someone, but hey~
Just like to note that I made this while listening to the ever entertaining chatter of those who have mics. So fun, haha.
edit: After our deliriously fun mock battles I realized it's a good thing I've got high TE defense. With the way I use the Plasma Gun, the splash reaches me, and at point blank a full volley (about, I don't know, 5 or so shots if I'm lucky) can reduce my AP by 3k or more @_@.