Think nibble. You can nibble off the cap of a cigar if you have to, I do it when I don't have a cutter handy.

Just pretend you're on a date and the girl is way out of your league but has the hots for you anyway, and nibble very tenderly and you will get what you want (in this case, the cap off a cigar, and just nibble off the loose tobacco if it's bothering you).