As much as I was disliking the list so far, I have to say Bret/Shawn deserves to be top 5 just for that segment where Bret called Shawn down to the ring for seemingly no reason at all, completely ripped him apart for 20 minutes, and then it just went off the air without any retribution from Shawn. That was insane. (And who can blame Shawn for being pissed off at something like that?) Every time they got together, you could tell they despised each other. And they got together a whole bunch of times. They feuded on and off for pretty much the entire year of 1997.
There was that segment I mentioned,
all of the January-February promos and build up between the two,
the promo where Bret turned heel against US fans, Shawn came out to tell Bret to get the fuck over himself, and Bret attacked Shawn's hurt leg from behind
the promo in Canada where Shawn announced he would be the special referee and if he didn't call the match right down the middle, he wouldn't be able to wrestle in the US again. So he would have to move to Canada and live next door to Bret. This also brought us one of the most classic lines of all time, "Bret, buddy, pal of mine, if you can't trust Shawn Michaels, who can ya trust?!!"
all of the buildup in October and November for Survivor Series. I'm sure there's some more I'm forgetting about.
I would put Bret/Shawn as #2 behind Bret/Austin.