We have done the biggest buck, biggest doe and smallest gets their dollar back. Wasn't too bad until most people wouldn't even give up a dollar for the pot. I have a buddy that at their camp they would put in 5 and for every shot they took another dollar went in. Biggest buck would take the pot. Had several years that the pot grew rather large. We have also done on the spot bets like height of a certain limb in a tree, or elevation difference between two points, closest to the bulls eye at a pretty decent distance.