I absolutely cannot pick one favorite line from this show. It's impossible. I refuse. *grins* Although the one about falling out the window kills me every time i watch that scene. the look on Lestrade's face is priceless. so here's a list of my all time favorite quotes from the show.
Sherlock Holmes: Sorry, gotta dash, I think I left my riding crop in the mortuary.
Sherlock Holmes: It means whenever the police are out of their depth — which is always — they consult me.
Sherlock Holmes: You were thinking. It's annoying.
Sherlock Holmes: Dear God. What is it like in your funny little brains? It must be so boring.
Sherlock Holmes: Anderson, don't talk out loud. You lower the IQ of the whole street.
Sherlock Holmes: ... Ha. Look at you lot. You're all so vacant. Is it nice not being me? It must be so relaxing.
Dr John Watson: Stop it! We can't giggle at a crime scene.
Sherlock Holmes: Careful! Some of those skulls are over two hundred thousand years old! Have a bit of respect!
Sherlock Holmes: Don't make people into heroes, John. Heroes don't exist, and if they did, I wouldn't be one of them.
John Watson: Are you wearing any pants?
John Watson: We solve crimes. I blog about it, and he forgets his pants. I wouldn't hold out too much hope.
Mycroft Holmes: We are in Buckingham Palace, the very heart of the British nation. Sherlock Holmes, put your trousers on!
DI Lestrade: And exactly how many times did he fall out the window?
Sherlock Holmes: I take the precaution of a good coat and a short friend.
Mycroft Holmes: That's the problem with the deceased. Late. In every sense of the word.