Each Autobot has a special ability specific to that character.

Bumblebee: Has a chance to collect more than one Energon Pack from a single enemy.
Crosshairs: Proficient with ranged weapons.
Drift and Grimlock: Earn 50% more Energon Shards after each mission.
Hound: Has increased defense.
Optimus Prime: Has increased melee power and critical hit chance.