A type of bottle/can opener.

Church key initially referred to a simple hand-operated device for prying the cap (called a “crown cork” or “bottle cap”) off a glass bottle; this kind of closure was invented in 1892. The first of these church key style openers was patented in Canada in 1900. The shape and design of some of these openers did resemble a large simple key. In 1935, steel beer cans with flat tops appeared, and a device to pierce the lids was needed. The same opener was used for piercing those cans. Made from a single piece of pressed metal, with a sharp point at one end, it was devised by D. F. Sampson, for the American Can Company, who depicted operating instructions on the cans. The church key opener is still being produced, sometimes as part of another opener. For example, a “butterfly” opener is often a combination of the church key and a serrated-wheel opener. (source)