Amara is the new Siren and appears to pack some very powerful abilities including a melee attack with six summoned arms, a self-projection that can attack, and Phaselock.
Zane is our wealthy and classy Operative class. Like Zero from Borderlands 2, Zane can throw out a decoy.
Fl4k is the our robotic beastmaster and can choose between three different pets, one of which is a Skag. According to the leak, each of the different pets will have its own moveset.
Moze is the soldier and can call in a giant mech that she will pilot. Other players can hop on the top of the mech and use the powerful mounted gun, too