In Mass Effect 3 for the PC, PS3, and Xbox 360, you can unlock the Drell Vanguard as a character to use in multiplayer, which is a powerful combat character with a larger health pool and the widest selection of weapons.
The Drell Vanguard is a rare card that you can get from purchasing any of the packs, however your chances are a lot better to unlock characters by purchasing Veteran and Spectre packs instead of Recruit packs.
Check out my other guide for more unlockable characters in Mass Effect 3 multiplayer.