When we announced that Microsoft had partnered with Amazon.com to provide Xbox Live Arcade games, we were quite excited. No longer did we have to buy packs of Microsoft points to get the exact game we wanted. Now there's another side effect from the deal - Amazon discounts.
Right now you can get Undertow for $5, that's 50% off, from Amazon.com. Undertow supports a three player online co-op mode through the entire campaign, one that we thought pretty well of too!
These deals only seem to last a day or two, so you might want to hope on it as soon as you can. In the meantime we'll keep our eyes peeled for other great co-op deals from the new Xbox Live Arcade store!