There's some pretty odd selections in this thread, but everyone gets their opinion I suppose. I only really watched Canada close enough to make worthwhile choices (I'm not sure how any of you watched enough to make accurate selections from more than 2 or 3 teams, but whatever).
Connolly - He never established himself after the pre-tournament injury
Olsen - I loved him at the U18, but I thought he was Canada's worst defenceman
De Haan - Another guy I've always liked, but he didn't elevate his game the way I expected (basically Tyson Barrie did what I thought De Haan could). He wasn't bad, but he didn't play to the level I thought he would
Roy/Visentin - Obviously
I hate to be one of those posters who just defends his own prospects, but I question those that were disappointed by Cowen. Perhaps your expectations were just too high. I thought he was very solid, and at times dominant defensively. It's the kind of thing you may only notice if you pay attention (or have Mackenzie/Maguire point it out). He is not a pretty player, at all, but he showed a lot this tournament.