An Enterprise security guard posted at the entrance to Roger Korby's caverns on Exo III in 2266, where the ancient android Ruk killed him before he could warn the ship.
Rayburn appears in What Are Little Girls Made Of?. He beams down to the frozen surface of Exo III with his fellow guard Matthews after Kirk becomes uneasy about the silence from Dr Korby's expedition.
Kirk orders him to stay at the cavern mouth and keep in touch with the Enterprise while the rest of the party goes below. After Matthews falls to his death, Kirk tries to raise Rayburn by communicator, but Ruk has already reached him and killed him.
With both guards dead, Kirk and Chapel are left alone among Korby's androids, and Ruk later imitates Kirk's voice to send a reassuring message to the ship. He was played by Budd Albright.