Best add-ons for wii (not in order):

1. GC controller/ wavebird
2. Rechargeable Batteries for wii-mote
3. GC Memory Card (if you play GC games)
4. Wii Balance Board

do not get those perpherals which make you wii-mote look like sth (cooking mama set/ sports etc), they are useless and it would be more fun using your imagination