www.msworld.org has an MS Cognitive Game that I find nice and challenging called the Case of the Missing Matches. It is a card style matching game, looking for pairs of cards... levels are easy, medium and hard... I do better than average on easy and medium but have yet to successfully complete a round on hard before time runs out.
The main link on the main page is a video from the ECTRIMS conference in Germany from mid September, but they have a search bar, TYPE: case of missing matches (the "the"'s throw off the search, so leave them out.)
you do need to join msworld.org, but it is free, has lots of stuff to check out and the video game is free as well.