Coffee. Buttered popcorn and cotton candy are gross, but coffee and licorice actually get spit out. Actually, I just avoid the brown and black ones altogether, even though it means I sacrifice the chocolate ones.
EDIT: Oops! I thought it was WORST flavor. Best would be the berry flavor ones.or most fruits. Just not coffee!
Watermelon, strawberry jam, strawberry daiquiri, cantaloupe, pina colada, one of the lemony ones but not the other, peach, juicy pear, and, like, four others. Oh, all the soda pop flavors, but especially 7UP and Grape Crush.