Caribbean Stud poker: post an ante and get five cards while the dealer shows one of theirs. Fold and forfeit the ante, or raise exactly 2x the ante to go to showdown. The dealer needs Ace-King or better to qualify — if they don't, the ante pays even money and the raise pushes. Beat a qualified dealer and the ante pays 1:1 while the raise pays a ladder from 1:1 for a pair all the way up to 100x for a royal flush. Provably fair.