#6 Any Stable/Tag Team
Seriously. Purists still hold the belief that the main event should be a singles match for the title, yet that has been ignored multiple times, and should have been avoided even more often.
Lest we forget, the very first Mania main event was a tag team match!
It is certainly within reason to wonder why the WWE has never even once returned to this idea. The Mega Powers, Hart Foundation, Legion of Doom, D-Generation X, Evolution, the NWO, a McMahon faction, the Nexus, the Shield, just an initial count of the teams and groups that have received a huge amount of television time from the WWE.
This is not suggesting that any of these teams or others should have closed the show in any given match, but for the WWE to seemingly never even considered building to another multi-man contest to close their biggest show is a big surprise.