Mass Effect 3: How to Unlock the Black Widow
In Mass Effect 3 for the PC, PS3, and Xbox 360, the Black Widow is a powerful weapon you can unlock for use in multiplayer games.
The Black Widow is an ultra-rare weapon, and can be found primarily by purchasing spectre packs for 60,000 credits.
Beating gold matches regularly is probably your best bet for acquiring the Black Widow, so try to find a team of people to play with regularly because completing gold matches on random is extremely difficult.
Check out my other guide for the complete list of unlockable weapons in multiplayer in Mass Effect 3.