If you happen to be in possession of a Wii and a friend -- and I'm pretty sure both can be acquired on ebay -- you really can't go wrong with Trauma Center: New Blood. It's hard to convey in words just how much fun 2-person co-op surgery is... that is, as long as it's a virtual body that you're horribly mis-stitching and filling full of laser holes.
Just be warned that, like all the Trauma Center titles, New Blood stars as a good time and ends as an outrageously brutal, white-knuckled marathon of abuse. I imagine I will really appreciate having that second player to help me when I'm fighting against the purple alien heart spiders (or whatever other bizarro sci-fi ailment Atlus came up with this time). I'm not 100 percent on this, but by the final stages these games may actually be more difficult than real surgery.
PS: No, not really. Hyperbole, man!