Most obvious stunt doubles

[Hamburger Pimp]

How about the original Batman series, and even the movie.  The Burgess Meredith double is my favorite, although the Cesar Romero is also quite obvious.

"Some days you just can't get rid of a bomb."

[yaddo42]

Some of John Wayne's stunt doubles in his later movies were pretty obvious. The most blatant one I can think of is the scene where he falls down a flight of stairs with Yvonne De Carlo in "McClintock!". The double is years younger and his build and psture are nothing like Wayne's.

The black guy that was Ace Freley's stunt double in "KISS Meets The Phantom" in one of the fight scenes is so obvious even through the makeup that Gene Simmons mentioned it on some show about their career on VH-1. Ace was reportedly to messed up to do many of his scenes. Just like they had to overdub all dialogue by Peter Criss because he was so hard to understand and wouldn't overdub the lines that needed to be done.