Some thoughts on puns:

The goodness of the true pun is in the direct ratio of its intolerability.  ~Edgar Allan Poe, Marginalia, 1849

A pun is a short quip followed by a long groan.  ~Author Unknown

A pun is the lowest form of humor, unless you thought of it yourself.  ~Doug Larson

Hanging is too good for a man who makes puns; he should be drawn and quoted.  ~Fred Allen

When one hears a pun, one feels as though one has been pushed over without one's consent.  ~Graycie Harmon

Puns are little "plays on words" that a certain breed of person loves to spring on you and then look at you in a certain self-satisfied way to indicate that he thinks that you must think that he is by far the cleverest person on Earth now that Benjamin Franklin is dead, when in fact what you are thinking is that if this person ever ends up in a lifeboat, the other passengers will hurl him overboard by the end of the first day even if they have plenty of food and water.  ~Dave Barry, Why Humor Is Funny

A lurking pun is the worst pun, one the offender has been waiting to spring on you.  ~Harry Mahtar

A pun does not commonly justify a blow in return.  But if a blow were given for such cause, and death ensued, the jury would be judges both of the facts and of the pun, and might, if the latter were of an aggravated character, return a verdict of justifiable homicide.  ~Oliver Wendell Holmes, Sr., The Autocrat of the Breakfast-Table, 1858

Punning and groaning are brothers.  ~B.F. Tucson

A pun is not bound by the laws which limit nicer wit.  It is a pistol let off at the ear; not a feather to tickle the intellect.  ~Charles Lamb, "Popular Fallacies: That the Worst Puns are the Best," Last Essays of Elia, 1833

A man who could make so vile a pun would not scruple to pick a pocket.  ~John Dennis, 1781

In the pun, two strings of thought are tangled into one acoustic knot.  ~Arthur Koestler

A good pun is its own reword.  ~Author Unknown

I'm an incorrigible punster.  Do not incorrige me.  ~Author Unknown 

If you trip over a pun in your speaking it's not so bad but to intentionally jump on one is a true offense.  ~Graycie Harmon

Puns are the gag hand buzzers of conversation.  It hurts a bit but everyone gets a good laugh out of it.  ~Grey Livingston

People who make puns are like wanton boys that put coppers on the railroad tracks.  They amuse themselves and other children, but their little trick may upset a freight train of conversation for the sake of a battered witticism.  ~Oliver Wendell Holmes, Sr., The Autocrat of the Breakfast-Table, 1858

A bad pun should be made through clenched teeth - Mary Jackson, New English Review