C♯m6 (also written D♭m6) is a minor sixth chord made of 4 notes: C♯, E, G♯, A♯. It sounds bittersweet, a little mysterious, and you hear it in gypsy jazz, film music and minor-key endings. It is the i chord of C♯ minor and turns up in 5 other keys.
The library above opens on C♯m6 with 14 shapes up and down the neck. Tap a shape to hear it, or play it one string at a time.