What are some of the Best Co-op Games?

I'm looking for some Co-op games to play with my friend. some wii and xbox games for summer time and maybe 1 or 2 PC games to play a little bit for the rest of the school year when we got time. Anyone have any suggestions on good games? We've already played a few games like portal, borderlands, all... show more I'm looking for some Co-op games to play with my friend.
some wii and xbox games for summer time and maybe 1 or 2 PC games to play a little bit for the rest of the school year when we got time.

Anyone have any suggestions on good games?
We've already played a few games like portal, borderlands, all gears of war.
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