So many to choose from.. Mine is probably Mr. Plow.
Most Helpful Girl
The one where Homer stops going to church1
Most Helpful Guy
There are so many great ones. One of my favourites, apt for this time of the year, is 'I Love Lisa' (season four, episode fifteen).
But, certainly, 'The Simpsons' lost its magic after the first nine seasons or so. It used to be very funny and clever, indeed.1