A punchy thought-provoking quote or line can oftentimes add to a speech by making a point. 

Below are some samples:

"Our speaker tonight needs no introduction. He / she did not show up."

"The first rule of holes: If you are in one, stop digging."

"Honest Politician: One that when he's bought, stays bought."

"There is nothing wrong with teenagers that reasoning with them won't aggravate." 
---Ron Howard

"I can stand brute force, but brute reason is quite unbearable. There is something unfair about its use. It is hitting below the intellect."
---Oscar Wilde

"Just because nobody complains doesn't mean all parachutes are perfect." 
---Benny Hill

"I used to think I was indecisive, but now I'm not so sure."

"A lie gets halfway around the world before the truth has a chance to get its pants on."
---Sir Winston Churchill

"Graduation speeches were invented largely in the belief that college students should never be released into the world until they have been properly sedated."
---Garry Trudeau

"Women are like cell phones. They like to be held and talked to, but push the wrong button, and you'll be disconnected."

"You're not drunk if you can lie on the floor without holding on."
---Dean Martin

"Asking politicians to give up a source of money is like asking Dracula to forsake blood."
---Cal Thomas

"I have found the paradox that if I love until it hurts, then there is no hurt, but only more love."
---Mother Teresa

"A kindergarten teacher is someone who loves children and hates zippers."
---Unknown

"Cleaning your house while your kids are still growing is like shoveling the walk before it stops snowing."
---Phyllis Diller

"When a husband brings his wife flowers for no reason, there's a reason."
---Molly McGee

"I've never been married, but I tell people I'm divorced so they won't think something is wrong with me." 
--- Elayne Boosler

"If you lose your temper, you’ve lost the argument."
--- Proverb

"Opportunities multiply as they are seized."
---Sun Tzu

"Never interrupt your enemy when he is making a mistake."
--- Napoleon Bonaparte (1769-1821)

"It's not the size of the dog in the fight, it's the size of the fight in the dog."
---Mark Twain (1835-1910)

"Good teaching is one-fourth preparation and three-fourths theater."
---Gail Godwin

"You can’t build a reputation on what you're going to do."
---Henry Ford

"What you do speaks so loud that I cannot hear what you say."
---Ralph Waldo Emerson

"The individual who knows the score about life sees difficulties as opportunities."
---Norman Vincent Peale

"You may have to fight a battle more than once to win it."
---Margaret Thatcher

"When one door of happiness closes, another opens; but often we look so long at the closed door that we do not see the one which has opened for us."
--- Helen Keller

"Whether you think that you can, or that you can't, you are usually right."
---Henry Ford

"You can discover more about a person in an hour of play than in a year of conversation."
---Plato

"Once you pour water out of a bucket it's hard to get it back in."

"If it were not for hope, the heart would break."
---mid 13th century English proverb

"A fool may give a wise man counsel."
---mid 14th century English proverb

"Diligence is the mother of good luck."
---late 16th century English proverb

"You got to be careful if you don’t know where you’re going, because you might not get there."
---Yogi Berra (1925-)

"A problem well stated is a problem half solved."
--- Charles Franklin Kettering (1876-1958)

"If everything is under control, you are going too slow."
---Mario Andretti (1940-)

"I don't know the key to success but I know the key to failure is trying to please everybody."
---Bill Cosby (1937-).

"The price of liberty is eternal vigilance."
---Thomas Jefferson (1743-1826)

"The problems that exist in the world today cannot be solved by the level of thinking that created them."
---Albert Einstein (1879-1955)

"A penny saved is ridiculous".

"You have to do your own growing, no matter how tall your grandfather was."
---Abraham Lincoln (1809-1865)