#3 The Rock costs John Cena the WWE Championship (WrestleMania 27)
The Rock was heavily featured in the promotion of WrestleMania 27, serving as the host of the entire event. He had a heated war of words with John Cena, spanning the entire Road To WrestleMania. It completely overshadowed Cena's WWE Championship match against The Miz.
The Great One was a constant presence throughout the show. He cut a really long promo at the start which featured some gems like him drinking "the people's water" and "When I say Yabba, you say Dabba".
The Rock also took part in some uncharacteristically unfunny backstage segments with the likes of Mae Young and Pee-Wee Herman. But his most significant contribution to WrestleMania 27 came at the very end after Cena and The Miz fought to a double count-out.
He restarted the match and immediately hit the Leader of the Cenation with a Rock Bottom, causing Miz to cover him and retain his WWE Title. The Rock ended up standing tall at the end of WrestleMania, as he took out The Miz as well.
It certainly was memorable, but some other hosts have been part of bigger and better moments. One of them included the People's Champion himself.