The User List

Mark Schlipper / The Luna Moth - site - Uses a Japanese Widow guitar with single coils. (info from source)

Greg Miller / Perish the Island - site - Greg uses a black fretted Hohner/Bartell bass. (info from source)

Larry Coryell - Don't know how long or on what recordings, but Coryell holds the distinction of being the only actual endorser and person in an ad for the Widow.

Jimi Hendrix - Reportedly used a Black Widow guitar in the studio (info from Gear Secrets of the Guitar Legends by Pete Prown and Lisa Sharken)

Jimmy Nolen / The JB's - Used a Black Widow guitar in James Brown's band til 1983 (info from 1000 Great Guitarists by Hugh Gregory)

Frank Zappa - Not sure when or where, but Harvey Gerst said so and that's enough for me.

Jeff Baxter / Steely Dan, Doobie Bros., Elton John - Not sure when or where, but Harvey Gerst said so and that's enough for me.