I'm a bit surprised nobody's mentioned Go. "At the end of round two, Bonnie Urseth's team has 250 points, and Charlie Siebert's team has 500 points. Our goal is 1,500 points, so now we'll play a 750-point round that won't matter one bit when we play the final round for 1,250 points."
OK, maybe not the worst, but why play a round that is, at that point, clearly going to have no impact on the outcome of the game? I suppose Family Feud was and is guilty enough of this with the first round in its various scoring formats, but at least it's disguised a little better when the dollar/point totals per round can vary based on performance.
It was a short-enough runner that I wonder if anybody knows just how many times on Go they ended up in the useless-third-round situation in the course of 79 episodes.