The scene that ranks among my favourites is short(less than a minute) and segues onto Kaufman's funeral. It is the moment that Kaufman(Carrey) realises that his last shot at survival is a falsehood. In that instant, Carrey exudes fear, acceptance, appreciation, humour, and something else that is hard to grasp; perhaps regret? Resignation? It's difficult to tell, but it is a potent moment that is compounded by the fact that during this expression, Carrey's gaze is firmly fixed on us/the audience.
Below are clips including the scene in question. If you've not seen the film, I recommend giving these a miss.
Here is a selection of videos pertaining to the film and Andy Kaufman...
Milos Forman (Official Site)
Man on the Moon(Official Site)
Milos Forman Wiki
Andy Kaufman Wiki
Man on the Moon Wiki
Man on the Moon trailer (YouTube)