I making my way through Call of Duty 4: Modern Warfare again. That second to last level in the missle silo with the time limit is tough. I usually average 200-300 deaths before I complete it.
My brother also just bought a Wii and I've been making my way through Mario Kart here and there. I can't get used to the motion control so I use the nunchuk so that it handles like the N64.