Everything related to Aaron, who was severely crippled by a distracted driver 6 years before the show. In one infamous moment, after being put through a relatively easy obstacle course while texting or drinking and failing miserably, the thoroughly humbled contestants are forced to all look Aaron in the eye and promise to never drive distracted again.
The episode in Ever where Angelina is dismissed from the show and shipped off to psychiatric care. It makes every time the show or its fans laughed about her driving into a "Funny Aneurysm" Moment.
Just to put this into context, every single time Angelina takes her run in any of the challenges, there is a distinct lack of music or joking between Andrew and Christine.