George Hample's transposition of a $1 and a $5 is my favorite of all the ‘in the spectator’s hands’ transpositions with currency.
This is the greatest switch of two bills that we have ever seen! Two bills are used, such as a five and a one. They are freely shown front and back. They are folded up, and you hold one, and a helper holds the other. When everyone’s hands are opened the bills have miraculously changed places. This can be repeated immediately.
This effect comes complete with George’s own routine and his own handling.