Very lightly used, a few times.

This is essentially an Ebow with a different design.

Description from the Internet:

The TC Electronic Aeon is an infinite-sustain device for guitar, bass and more that produces powerful, prolonged notes and swells of spaced-out sounds. Instead of being mounted at your feet like an effects pedal, Aeon puts the effect where it matters most – right in the palm of your hand. Providing instant access to an entirely new world of amazingly expressive guitar tones, Aeon lets you tap into soaring bowed arpeggios, vibrantly bouncing spiccato, volume swells, endless sustain and sweeping legatos that can easily be mastered using a variety of simple techniques.