S:

- Very high DPS, fast speed on bike, which leads to insane ranged frontal drivebys, and good self-healing.

- Her plasma cannon scales very well versus multiple enemies, which means that Iji is one of the best classes at anchor defense, and taking down healer combo teams.

- Very fast, tons of offensive and defensive options at all ranges, high DPS when up close due to the ball and slide tackle.

- He's a rifleman on steroids. Scope + very high burst damage + cloak = very hard to beat initiator/finisher.

- Dante has something for every situation. Roll cancel and gun cancel makes both his offense and defense scary in the hands of a pro.
A:
Literally everyone else except for...
B:

- Can be situational, but if you have willing teammates that will switch to other classes just so you can get some powers, the Giraffe becomes the X-factor on your team, able to fill in any gaps.

- Pretty bad without a healer, but is probably S tier with one. Marine + Psychopath offers much higher damage potential when paired up with his flamer, while Marine + Drool Warrior offers much better mobility control.

- Obviously bad with bad stats, and godlike with good stats. Gauss Rifle competes in the top 5 ranged weapons in the game (Plasma Cannon, Shepard's Widow rifle, Mojo's mech eye lasers, Gauss Rifle, Saniman's flamebreath). Super Sledge is single handedly the best melee in the game. The only thing keeping Vault boy down is that weird stat allocations can prevent him from being totally dominant (low hp, speed, perception, etc).