Originally Posted by coolx
Anybody having problems with stuff staying stuck might want to try a very sturdy, strong holding adhesive called E 6000. It goes on clear, you need apply very little to a clean surface and it sticks like crazy to just about anything. I've found it at Academy sporting goods in the marine department. IMO, I think every do-it-yourselfer should have this stuff in their toolbox... 
In the event you need to remove this stuff from your headlights, the clean up does not sound easy or fun...
CLEAN UP & REMOVAL RECOMMENDATIONS:
Uncured E-6000® can be cleaned by using small amounts of solvents such as Acetone, Tolulene or Naphtha.
Cured E-6000®
requires scraping or cutting away product with sharp knife and use of mineral spirits (i.e. gasoline, lighter fluid, lacquer thinner) to soften product.