Mass Effect 3 this week, aimed at fixing exploits and patching in some gameplay balances. A large deal of the changes affect multiplayer powers and enemy behaviors, like Banshees being stuck in a teleport routine and being able to grab Geth Pyros over cover.
Game crashing bugs have also been addressed, including a nasty Bionic Charge glitch that would render the match unplayable and the Singularity power has been redesigned. BioWare expects the patch will be available this Thursday, but nothing is set in stone: Xbox 360 and PS3 players will be automatically prompted to install the patch, while PC users will need to manually install the update through Origin.
For the full list (it's a full list) of changes, head on over to the BioWare forums.