According to Gene Kranz in his book Failure Is Not an Option, "When reporters asked Shepard what he thought about as he sat atop the Redstone rocket, waiting for liftoff, he had replied, 'The fact that every part of this ship was built by the lowest bidder.'
So it seems to be Alan Shepard.
Also John Glenn said it:
“I guess the question I'm asked the most often is: "When you were sitting in that capsule listening to the count-down, how did you feel?" Well, the answer to that one is easy. I felt exactly how you would feel if you were getting ready to launch and knew you were sitting on top of two million parts -- all built by the lowest bidder on a government contract.”