I would say the best hidden gem for me is Flowerworks, the game developed by the user shams (he hasn't been online in a long time). It is probably difficult to see the appeal of the game in images or even video, but the flower works puzzle stages are very fun, use the IR pointer controls very well, and become quite challenging. It is a lengthy game, I think it took me about 12 hours to complete, and there is still a lot more to do after beating the main game. In Europe the game is only 500 points, and I highly reccomend the game at that price. In Americas it is a 1000, which it is still worth, but I would make sure you have watched some videos just to make sure the game interests you somewhat.
Art of Balance is a really highly rated WiiWare game, but I don't hear it talked about very much. It is an extremly polished game, very fun, a good value (I think it is 600 or 800 points). I also really like the local vs. mode.
