ilovefuzz.com

For humbucker guitars, I usually go classic cheesy and bang out "You Shook Me All Night Long". And then tune the low E string to D and bust out the main riff from Rage's "Freedom".

For just about any guitar, I also run through some pretty Pink Floyd chord progressions with a clean amp.

Depends on the effect or gear I'm trying out. Keep in mind this is for bass

Amp or overdrive:
Dragonaut, Take the Power Back, Israel's Son, NIB

Fuzz:
Sabotage and Gratitude, Weezer - Tired of Sex, various Ben Folds Five riffs

Modulation:
For the Love of Money, Gratitude, various Tool riffs, various Isis riffs

Delay: Tool and Isis riffs, No Shelter