I've been doing a little research, and find that many companies claim their's is the strongest.
The strongest I have tried were Fisherman's Friend, and those mints burned.
I've read that C.O. Bigelow Peppermints are very strong. And another one that looks rather artistic called momints, which are liquid mint, is supposed to be as well. Momints has a wikipedia page: http://en.wikipedia.org/wiki/Momints They look pretty, but somewhat like the VX nerve-gas modules from The Rock movie.
It's like the hot sauce pursuit of the hottest. What mint is the mintiest?