I like Gauss well enough. His '1' is lots of fun and his '3' is a pretty good "emergency button" for when you're getting mobbed and need to drop a bunch of guys suddenly - didn't really spec for his '2' and kept forgetting to use it, but it didn't seem to do me any harm.

I feel slightly underwhelmed by his '4' - Redline ability. I've triggered it a bunch of times, and I'm still not actually sure what it does apart from activate particle effects and change his armour. I know it must being doing something as I've read the description and the progress bar on the right counts up and down.... but it's far more passive than I expected. Unless you're spec'ing VERY heavily into ability power it hardly seems worth bothering with. *shrug*