FLOCK! may only be a week or two old, but the two player local co-op game most likely had a hard time selling at its $15 price point . That's where Amazon comes in! Thanks to their brand new Xbox Live Arcade store you can snag FLOCK! for a $5 off it's normal price.
Keep an eye on the site as we'll have a co-op review of this sheepingly interesting title sometime next week!
Another promotion Amazon is running - purchase a 1600 MS Point code from Amazon or a 4000 MS Point code from Amazon and you'll get $5 or $10 credit respectively towards another code purchase from the site. So you could pick up 4000 points and get FLOCK! for free! Score! Notice all the !? Ok then....
Source: Amazon.com