In Mass Effect 3 for the PC, PS3, and Xbox 360, you can unlock the Quarian Infiltrator as a character to use in multiplayer, which is good against Geth and other synthetics because of the sabotage ability.
The Quarian Infiltrator is an uncommon card that you can get from purchasing any of the packs. Your chances are typically better to get characters with Veteran and Spectre packs instead of Recruit packs however.
Check out my other guide for more unlockable characters in Mass Effect 3 multiplayer.
