James R. Rummel of Hell in a Handbasket has a post about early handgun bayonets. The Elgin Pistol Cutlass (above) was a single-shot pistol available in the U.S. in various calibers starting in the 1830s. It's basically a built-in machete that served to clear away brush while tramping out in the wilderness:
Instead the guns were designed to be used as brush cutters in dangerous territory. The heavy knife would clear away the jungle, while the pistol would be ready if enraged animals or hostile natives suddenly sprang from the bracken.
At the link, you can view pictures of a bayonet that could be fitted onto World War I-era British revolvers.
http://hellinahandbasket.net/?p=4828 | Photo: American Firearms