RE4:Wii is a no-brainer. It's cheap and it's really a new experience with point and shoot over the original version on the Cube. I would wait on reviews of BWII and see how that goes. That title looks really, really fun. Raving Rabbids is OK, but 2 is coming out very soon so I'd go that route instead....
Medal of Honor: Heroes is out soon, too. It looks like it will be a lot of fun. Does it have an expiration date? There are so many games coming out between now and the end of the year it would be a shame to burn it on a game like WarioWare when you have things like SMG coming down the pipe...