A number of dates in the Franklin Half Dollars include what are known as "Bugs Bunny" varieties. These are caused when the dies clash and a small, buck-tooth spike appears on Franklin's upper lip. The most famous of these is the 1955 "Bugs Bunny" but others, such as the 1956, exist. They are not particularly rare, but they can be found unattributed because they are subtle. Numerous high-quality Mint State examples exist, including dozens in Gem.
Bugs Bunny Half Dollar