Sleuths point to Mass Effect 3, Shattered Steel.
The game BioWare teased earlier this afternoon could be Shattered Steel or Mass Effect 3.
A barcode tweeted by the developer was scanned to reveal a binary code. RockPaperShotgun deciphered this to give the number 55.845, otherwise known as the atomic weight of iron, a material that can be turned into steel.
Shattered Steel was a 1996 game by BioWare that was fast-paced and involved mechs destroying each other. Multiplayer was a key part of it.