How about three for the price of one?
The first is unforgivable, and for use in meetings - I think its wonderful, but have never disliked someone enough to use it:

"I see you've set aside this special time to humiliate yourself in public."

The second is good for parties, when alcohol and a laugh will soften it:

"The fact that no one understands you doesn't mean you're an artist."

The third is a put-down for use by women who are being pestered:

"How many times do I have to flush before you go away?"

But my favourite put-down came from a friend of mine to a smoker on a sardine-can crowded commuter train many years ago:
Friend: "Please would you mind not smoking right under my nose."
Smoker: "This is a smoking compartment, mate."
Friend: "That's a privilege, not a right."
Smoker extinguishes cigarette sheepishly. You had to be there.

dxb.