Bioware and EA will be releasing Leviathan, a DLC for Mass Effect 3 that is focused on story, in a hardcore way apparently. Shepard will learn more information and history about the Reapers as he/she takes the Normandy to a downed ship on a distant planet. You will be able to guide Shepard underwater in search of an entity that could help stop the Reapers. Included in this DLC, are two new guns, the M-55 Argus rifle and the AT-12 Raider shotgun.
For the nice price of $9.99, Leviathan will be available for download later this summer via XBL, PC, and PsN.