(G=Green, R=Red, Y=Yellow, B=Blue, O=Orange)
At the main menu in Guitar Hero World Tour insert these cheats on Wii:

ATT Park

YGRRGBRY

Aaron

BRYYYYYG

Always Slide Mode

GGRRYRYB

Automic Kick Drum

YGRBBBBR

Best Buy Kid

GRBGRBBG

Different Flame Colors

GRGBRRYB

Different Gem Colors

BRRGRGRY

Different Star Colors

RRYRBRRB

European Kid

BRBRYYYG

Hyperspeed Mode

GBRYYRGG

Invisible Characters

GRYYYBBG

Invisible Instruments

RRBYGGGY

Line Six Notes

GRYBRYBG

Performance Mode

YYBRBGRR

Rina

BRGGYYYG

Unlock All Songs

BBRGGBBY

Vocalist Breathes Fire

RGGYBGYG