Unlock Darth Vader's Tie Fighter:
Defeat Darth Vader Bot in Multiplayer mode.

Unlock General Grevious's Starfighter:
Beat General Grevious Bot in Multiplayer mode.

Unlock Master difficulty for Anakin:
Beat Obi on any difficulty.

Unlock Master difficulty for Obi-wan:
Beat Anakin on any difficulty.

Unlock Millenium Falcon:
Beat the Solo Bot in Multiplayer mode.

Unlock Slave I:
Defeat Fett Bot in Multiplayer mode.

Unlock X-Wing:
Beat the Luke Bot in Multiplayer mode.