A whimsical thing: the Oxford Electric Bell, pictured here, is a battery-powered device that has been running (almost!) continuously since it was built in 1840. A clapper on a pendulum rocks from side to side between two metal spheres, driven by electrostatic forces. The bell is powered by a pair of mysterious batteries, the composition of which is unknown.
However, because it sits behind two layers of protective glass, the bell is inaudible.