Maya is pretty good, since that action skill adds almost all the elemental effects and you have bouncy bullets (at the singularity)
Salvador deals essentially double damage at all times, or worst case scenario - just has a slag offhand
Axton ... people say he's good, but I'm not seeing it beyond slag on turret. Excluding infinite speed glitch.
Zer0 ... While cool, doesn't have any active slag skills. But B0re can be broken and accidentally OHKO OP8 bosses
Gaige is fun, but also lacks built-in slag; but the bouncing bullets with Anarchy can cause a lot of chaos, especially with graphically intensive non-rocket guns... also has the least clutch class skill so, but he's also not weak, so you can just summon your bot whenever you feel like it and it's never a mistake.
Kreeeeeegi ... idk, never tried, he wasn't in the game when I was playing it... back in 2012.
im so sorry lokarin ---
"I live my life 3 videogames at a time. Nothing else matters. Not the mortgage, not my clan and their BS. For those 3 games or less, I'm free."