These insults are from an era before the English language got boiled down to  4-letter words. Insults then, had some class! 
1.  "I  am enclosing two tickets to the first night of my new play;  
 Bring a  friend, if you have one."
     George  Bernard Shaw to Winston Churchill.  
 "Cannot  possibly attend first night, I  will attend the second...If  there is one."
     -  Winston Churchill, in response.   
 2.   A  member of Parliament to Disraeli: "Sir, you will  either die on the gallows, or of some  unspeakable  disease."
     ·  "That  depends, Sir," said Disraeli, "whether I embrace  your policies or your  mistress." 
  3. "He  had delusions of  adequacy."    -  Walter Kerr 
4. "I  have never killed a man, but I have read many  obituaries with great  pleasure."
     -  Clarence Darrow
 5.  "He  has never been known to use a word that might  send a reader to the  dictionary."
     -  William Faulkner (about Ernest  Hemingway). 
6."Thank  you for sending me a copy of your book; I'll  waste no time reading  it."
     -  Moses Hadas
7. "I  didn't attend the funeral, but I sent a nice  letter saying I approved of  it."
     -  Mark Twain
 8. "He  has no enemies, but is intensely disliked by his  friends.."
     -  Oscar Wilde 
  9. "I  feel so miserable without you; it's almost like  having you  here."
     -  Stephen Bishop
10."He  is a self-made man and worships his creator."
     -  John Bright
 11. "I've  just learned about his illness. Let's hope it's  nothing  trivial."
     -  Irvin S. Cobb 
 12. "He  is not only dull himself; he is the cause of  dullness in  others."
     -  Samuel Johnson 
13.  "He  is simply a shiver looking for a spine to run up."
     -  Paul  Keating
14.  "In  order to avoid being called a flirt, she always  yielded  easily."
     -  Charles, Count Talleyrand
 15.  "He  loves nature in spite of what it did to him."
     -  Forrest Tucker 
 16.  "Why  do you sit there looking like an envelope  without any address on  it?"
     -  Mark Twain 
17. "His  mother should have thrown him away and kept the stork."
     -  Mae West
 18.  "Some  cause happiness wherever they go; others,  whenever they  go."
     -  Oscar Wilde
 19. "He  uses statistics as a drunken man uses lamp-posts... For support rather than  illumination."
     -  Andrew Lang (1844-1912)
20.  "He  has Van Gogh's ear for  music."
     -  Billy Wilder
21. "I've  had a perfectly wonderful  evening.  But  this wasn't  it."
     -  Groucho  Marx.
22."He  has all the virtues I dislike and none of the  vices I  admire."
     -  Winston Churchill