Worst/best moment?

In your opinion, what's the most heartbreaking and sad sentence/event that occurred in the whole series and what's the best one and why?

Me and my friends wanted to do a tier list of the worst/best moments in house and we want to make sure we have all of them (we're re-watching together to make sure we don't lose anything).

The one that wins for me right now it's when Wilson tells House that they're no longer friends after S4 finale, but I'm not sure about it being the worst.