Non licensed general theme pins like they made in the 60's and early 70's.
If we are talking licensed themes - too late - Saturday Night Fever, Bee Gees - way too late. LOL
Many others and many already mentioned.
If they would have made Men In Black, that would be one I think would still sell / trade today.
Back to the Future if it would have been done a little better and with a game corresponding to each movie would make a neat little collection.