Majin-Tenshinhan on 16 April 2008
Resident Evil 4 Wii Edition (If you haven't played RE4 on the GC or PS2)
Super Mario Galaxy
The Legend of Zelda: Twilight Princess (If you haven't played it on the GC)
Metroid Prime 3: Corruption
Mario Kart Wii and Super Smash Bros. Brawl are definitely worth getting, but judging from your sig I'm assuming you aren't able to get either at the moment.
If you want to have fun with friends, Mario & Sonic at the Olympic Games.
