Took a couple of large stickers off of my bike about a week ago and it left quite a bit of residue unfortunately. Even tried alcohol to take it off with, which I use to remove almost every kind of adhesive on everything else.
Originally I went out to buy some 'Goo Gone' becuase everyone knows that stuff works great, but when I stopped at Advanced to get some I found out they don't carry it, but instead they had this spray on stuff pictured below.
I just let it set a moment or two then for the most part it wiped right off, and the tough spots came off with a fingernail. Anyways, it's clear to see with the pictures I have below that this stuff works great.
Before-
After-