Half Dollar/English Penny
This is the set to start with if you've never performed the trick before. Because the coins are different colors but the same size, the handling is easiest and allows for other creative interludes, such as making the coins change places and vanishing it at the end.
US Quarter and Penny
In this version the two coins are of different sizes, and BOTH coins used are part of the common change carried around in the USA. That makes this version the most innocent and impromptu looking. Just be careful, as the coins are so small that it's a little less visible than the larger version.
Sun and Moon
When you see "Sun and Moon" versions, this essentially is an effect with an outer shell that fits over a double-sided coin, allowing for super visual changes and sequences.