Free: Contests & Raffles.
The last 14 states to officially outlaw dueling did so in 1859 in the US and 1844 in England. The percussion cap came into use in the 1840's so it saw only limited use in dueling. The flintlock was in use during the heyday of dueling.
27. Missed the first plastic pistol, the Columbine question, and the Crockett.