A Ferengi head on a key chain
A tribble key chain
A key chain was a ring or chain that could be used to connect all of a person's keys together.
In 2022, when an alternate version of James T. Kirk and La'an Noonien-Singh stole a Dodge Challenger Hellcat, Kirk sat in the driver's seat and examined the car keys, as he held the key chain in his hand, looking at it; trying to figure out which key was meant to start the engine. (SNW: "Tomorrow and Tomorrow and Tomorrow")
According to an account that was anything but canon, during a song that was played by a Post-Mainframe Acid-Cardassian Ten Forwardcore band on the bridge of the USS Enterprise, there's a part of the song in which the lyrics refer to Ferengi. As William T. Riker sings that part of the song, an image of Quark can be seen on the viewscreen holding a heart-shaped key chain. (VST: "Walk, Don't Run")
According to an account that was anything but canon; on a malfunctioning holoprogram, Quark was trying to sell a propaganda holographic program to Garak. He even told him he would throw in half-price root beer floaties and a key chain. (VST: "Holograms All the Way Down")
The keys for the Cerritos captain's yacht were kept on a tribble key chain. (LD: "Terminal Provocations")