What's your favorite Monty Python sketch and why?

Confuse a Cat sketch.

whowasthatmaskeman beat me to it, but let me give you a killer exchange from "The Cheeseshop [a distinguished gentleman entirely versed in cheese varieties becomes frustrated that nothing is in stock...until: [Gentleman] What about brie? {Salesclerk} It's a bit runny, sir. G: that's alright, I'll take it anyway. S: It really is VERY runny, sir. G: I don't care HOW bloody runny it is, just give it to me! S: Oh, sorry, sir, the cat's just eaten it!
The runner up is the Idiot, smacking his fists together while standing in a stream wearing his silly sweater says: "I would tax anyone standing in water!"

i like the ministry of silly walks because its just so random XD

The Parrot Sketch...

The Piranha Brothers, too funny.

"Once, one Sunday I told him my parents were coming round to tea and would he mind very much not nailing my head that week and he agreed and just screwed my pelvis to a cake stand"

Its not a sketch , but the old guy clapping as he hangs in chains , while knights of the round table dance and sing gets a hoot out of me every time.
P.S. "we've got lumps of it 'round the back"

That'll be the peasant asking for democracy in the quest for the holy grail.

monty..monta...its like riding a bike through the sketch of your thought!

the sketch in the flying circus when the fat man explodes...... :) 'its only one paper thin wafer' 'f**k off,im full!'....such a classic scene!!!.....:)

The four yorkshiremen. Very funny, each trying to outdo the others with their tales of hardship in youth. Reminds me of my dad, and his brother!

Two words...

"Morning, Bruce!"

In one of my former IT jobs, a group of us (more or less the "office clowns") collectively came to be known as the Bruces because of that sketch.

"There is NOOOOOOO...Rule 6!"