I pulled all mine off. Decided helmet stickers are mostly vulgar and stupid. Goo gone works great, but I just left the remnents. Who cares, it's just a ugly helmet anyway.
Depending on the finish be very careful. I've used these, Goof Off, (isopropyl) rubbing alcohol, graffiti remover wipes, and (BE VERY CAREFUL WITH) break cleaner. Break cleaner removes gunk other leave behind along with the finish of the surface and can cause watery eyes, runny nose, shortness of breath, low test scores, bad breath, and your taxes to go up...a lot. So be careful with it.