The US Office - when Michael leaves. Yeah there’s some good stuff afterwards but it’s never the same and it would have been a nice end point.
Peep Show - Mark & Sophie’s wedding at the end of series 4. It’s still funny after that obviously but less and less so as it goes on and that episode is absolutely perfect and sums the show up brilliantly. The end line ‘yeah, stick it on the bill’ and them driving off is so good.
The Simpsons - “you know what lads, 10 seasons is a nice round number, let’s just call it a day shall we”
What are some more please?