I fondly remember him as the curmudgeonly FBI agent Bill Maxwell in the TV series The Greatest American Hero, with William Katt as the bumbling Ralph Hinckley and the lovely Connie Sellecca as Pam Davidson. Hinckley is an innocent schoolteacher who suddenly comes into the possession of a superpowered alien suit but loses the instruction manual. It was a fun show, and Robert Culp's performance in it was one of the big reasons I enjoyed it so much.
Culp also starred in a cult favorite episode of the original The Outer Limits, "Demon with a Glass Hand," written by one of my favorite authors, Harlan Ellison.
Culp had an incredibly lengthy acting career, appearing in TV shows and movies since the 1950s and working steadily ever since.
May he rest in peace.