As for verbal snarkiness, of course the ineffable Cecil ranks as a master. (The ‘cornflakes’ line…::wipes away a tear of appreciation:
But a Dorothy Parker classic:
A luscious but callow Young Hussy runs into Dorothy Parker in a doorway at a formal gathering.
Hussy: (with a mocking wave) " Age before beauty!"
Dorothy Parker: "Pearls before swine. " …said before smiling and sweeping through the doorway
Veb
I wish you guys would stop splitting the hairs of the bush you’re beating around…
How about: “you’re not even interesting enough to make me sick”?
By Lloyd Bentsen. “Senator, I served with Jack Kennedy. I knew Jack Kennedy. Jack Kennedy was a friend of mine. Senator, you’re no Jack Kennedy.”
Spelling is perfectly okay to pick on in the right situation. In GD recently, I was told to stop being “nieve” about an issue. Twice. If that’s not fair game, I don’t know what is. All I wrote was “Don’t use insults you can’t spell,” which I think is good advice on message boards and in life.
By the way, Cecil’s great quote was actually “If ignorance were cornflakes, John, you’d be General Mills.” 
Not one that I’d ever have occaison to use, but it’s my favorite:
Jean Harlow: Why, you’re Margott Asquith, aren’t you?
Margot Asquith: No, my dear. The t is silent, like in Harlow.
He has delusions of adequacy.
Why split hairs when they can be easily shaved? 
Regarding sentence construction-*This is the sort of English up with which I will not put.[i/] Winston Churchill
Churchill was pretty good at put downs. Or he had a clever biographer. A lady whose title escapes me at the moment: “Winston, if I were your wife, I’d poison your coffee.” Churchill: “Nancy, if I were your husband, I’d drink it.”
Dorothy Parker had a jillion, too. My two favorites are (probably paraphrased) :“The problem with this book is that the covers are too far apart” and “As an actress, she displays the full gamut of emotions from A to B.”
My friend Darren, about an annoying mutual acquaintance - “When you think that the molecules that went into making that guy could have been used for something USEFUL, like a couple hundred mosquitoes…”
Darren again about a twit: “He has the mind of an excruciatingly intelligent houseplant.”
Churchill’s legendary insults, real or not, were supposedly exchanged with Lady Nancy Astor.
A recent salvo
struck me as an effective put-down. Erudite, original and no face-saving humour.
That’s good, but it’s still not Shakespeare. Let’s give the next batch of monkeys their typewriters.
If the poster starts to use spelling and grammar mistakes as a put down without a follow up to the debate at hand, I usually find this to be the end of the debate. As well as pretty damn shallow. It’s a lose lose for that kind of poster.
“[You are] not even wrong.” - Wolfgang Pauli
My favorite is a Bill Hicks Quote:
(to a Waffle House waitress who asked him why he was reading)
“I guess I read for a lot of reasons, the main one would probably be… So that I don’t end up a fucking waffle waitress.”
I’m hesitant to share this, as it’s my favorite and I like to reserve it for those extra special occasions.
I swiped it from a newsgroup posting years ago. Wish I could credit the originator.
[George Costanza]Oh yeah? Well, the Jerk Store called… they’re running out of you![/GC]
One of my favorite Churchill put-downs was when some snooty old society dame accused him of being drunk, to which he replied, “My good lady, I may be drunk, but you’re ugly, and I’ll be sober in the morning!”
Heh. Now that is good.
levdrakon. I can’t believe I’m doing this, but… (Begins Cinematic Slow Clap)
Hee. My favorite bit: “If you were dropped naked in a field of horny clues, you still wouldn’t have a clue.”
Taken from real life at a Black College: Two students were in the middle of a very public break up on the dormitory steps, with like, 100 people looking on. After a long harangue, the guy says to the girl: “I know you’re cheating, and one of these days I’ll catch you with your pants down!”
Girl goes, “If you do, be sure you kiss my ass!”
Shoeless, I kinda’ like this one:
“It’s better to read the whole thread before posting and be thought a fool than to fail to read it and remove all doubt.”
My all-time favorites come from Bette Davis. The feud between Bette Davis and Joan Crawford was legendary. She said of Joan, “I wouldn’t piss on her if she were on fire.” Classic. When asked why she was at her best when portraying bitches, she said, “Why am I so good at playing bitches? I think it’s because I’m not a bitch. Maybe that’s why Miss Crawford always plays ladies.” Upon hearing that Joan Crawford was dead, she said, “You should never say bad things about the dead, you should only say good… Joan Crawford is dead. Good!”
Hey! I don’t go to where YOU work and knock the dick out of your mouth.