For sheer surreal absurdity and quality thematic juxtaposition, I always prefer the FC stuff over the films.

My number one would have to be the Buying a Bed sketch from Series 1 Episode 8. It's just so absurdly hilarious, gets me every time.

My other top favorites, in no particular order, would be The Fish-Slapping Dance, The Ministry of Silly Walks, The 'Blancmange from Space' Story from Series 1 Episode 7, The Mr. Neutron stuff from Series 4 episode 5, the 'Pither Bicycling story' from Series 3 episode 8, Upper Class Twit of the Year, Dirty Hungarian Phrasebook, Dennis Moore, Cheese Shop sketch, and The Funniest Joke in the World. There's also The Philosophers' Football Match, even though it comes from the German show.

Incidentally, I would have included the Hollywood Bowl concert film in this list. It may not be a 'proper' film but it has some of the best MP stuff, like the Four Yorkshiremen sketch, the Sit on My Face barbershop quartet and the Comedy Lecture.