In the winter back East we used to bring a feather into a bar and bet people we could "throw the feather over the building". Once people put their money down we'd go outside, pack the feather in a snowball and, yup, throw it right over the building.
We'd make a 1/2-inch hole in a bar coaster and bet people that we could "push a 50-cent piece through the hole without the coin touching the hole at all". Once people put their money down you just take a pencil, stick it through the hole, and push the 50-cent piece laying on the bar with it.
We had a bunch of other ones but I can't remember them at the moment.