Really quick, devastating putdowns:

Ignoring Oscar Wilde today, I'll mention a few favorite cases where someone came up, on the spot, with a brief but devastating response.
Bertrand Russell had explained, in a symbolic logic class, that if you start by assuming a false statement is true, you can prove anything. A student having trouble with this said, "Assume one equals two. Prove you're the Pope!" Russell said, "It's well known the Pope and I are two; therefore the Pope and I are one."
Someone once said to George Bernard Shaw, "Do you know that sugar and sumac are the only words in English where an initial "su" is pronouced like "shu"? "Shaw responded, "Sure."

And in the early days of computers four friends had just come together when one said "I've just been appointed head of the [state university] computer center." The youngest and brashest of the others said, "WHY?" The four of them stared at each other for a minute or two. There was nothing to say. They all walked off.

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