Jets vs Colts has to be the most major upset.
Although living in Wisconsin and a huge Packer fan, I liked to watch the AFL. They were a lot more wide open than NFL teams. I knew the Jets had a good team, and Namath was a better QB than anything the Colts had...including Unitas who was fading at the time.
A lot of my friends dismissed the AFL, and all the...uh...experts picked the Colts to win by a big number. That might have the best I've felt from watching a non-Wisconsin sports team win. Didn't like the Colts...they were too good.
Second to the Giants denying the Pats a perfect season according to this article. And one could probably drink beer and argue about that all night long.
I’ve never really been a Jets fan, but I will always love Joe Namath.