*This is in no particular order*
I found it so hard to finalise a top ten list and honourable mentions must go to Roz and the Schnoz, The Doctor is Out, Flour Child and Halloween which all almost made the cut (also I've selected part 1 for Something Borrowed .. but it counts as both parts).
Have loved looking at everyone else's lists - very interesting to see the different choices we all have.
My Coffee with Niles - outstanding writing and delivery; Three Valentines, Act 1 - best comic acting in 7 minutes, ever; Daphne Hates Sherry - "oscillates"; First Date - chopping vegetables in rhythm. Wish I could list more than 10 - I would include IQ, Back Talk, Dark Side of the Moon, and Daphne Returns.
I love the ones where they try to be something they're not -- i.e. Jewish, gay, black, bad students, etc. The smoking episode, ham radio and dead seal episodes were just hilarious. This list is in no particular order.