We have a guy in N. Illinois comes to an open mic night who plays guitar (or autoharp) shakes a tamborine with his strumming hand, sings (or plays harmonica) and plays a double bass with his feet.
The bass lays on its side clamped in a homemade rack which includes a chair so that the bass rig is captive, he takes off his shoes and stops the string with his left foot and plucks it with his right big toe.