Mercifully, I’ve erased the memory of Lee Majors’ “singing” from my memory. He was absolutely awful in the “Six Million Dollar Man” episode that introduced Jaime Sommers as the Bionic Woman.
He sang three or four variations of the closing ditty. I believe he wrote the lyrics as well, but was forbidden from mentioning any of the show’s elements, which is why “tossed salad and scrambled eggs” came about instead.
New Tricks, a British cold case cop show that you can see on some PBS channels, has a theme song that is sung by Dennis Waterman, one of the original four stars and the only one of the original that is still on the show (as of 2013 I think).