BioWare will be hosting an "N7 Challenge Weekend" this weekend for Mass Effect 3's multiplayer. By playing the game's co-op missions on the Xbox 360 and PC, you can unlock bonus in-game items.
This Challenge Weekend is dubbed "Operation Goliath." If you beat the Reaper faction on Silver difficulty or higher, you and your squamates will get a Commendation Pack. Each pack contains a random N7 weapon.
"Originally only available as single-player weapons via the N7 Collector’s Edition, these multiplayer variants will be exceptionally rare and are NOT obtainable through regular purchasable Reinforcement Packs," said BioWare. "The Commendation Packs will contain one of the following guns at random: (1) N7 Crusader Shotgun, (2) N7 Eagle Pistol, (3) N7 Hurricane SMG and (4) N7 Valiant Sniper Rifle."
There will also be a community-wide challenge in effect. If the player community kills over one million Brutes this weekend, every player will receive a Victory Pack.
The Challenge Weekend begins tonight at 5PM PST. It'll conclude on Monday at 5AM PST. Rewards will unlock on Tuesday at 5PM PST. You'll need to open your reward pack within a week of receiving it. Also note that you need to turn data tracking (options->online->upload gameplay feedback) to be eligible to participate.
On a related note, BioWare also released an image with some statistics about ME3's multiplayer. Check it out below.