I love the moment after Megatron has killed Bumblebee and we've watched him fall, and we're all crying (at least on the inside), and everyone is shocked and angry because it's Bumblebee!

Then Optimus turns to Megatron with this look on his face and everyone watching says:

"Aw dang. You gonna pay for that." 

Then Optimus beats him up. 

10/10 

Closely followed by the moment that Bumblebee kills Megatron and says a really moving line without even realizing that everyone can understand him. (I mean everyone could always understand him, but you know what I mean.)