Some of the wittiest things I've heard came from bumper stickers. I think it's because space is so limited--you have to keep whatever you're saying short and to the point. Anyway, here are some of my favorites:
"Government philosophy: If it ain't broke, fix it until it is broke."
"Be nice to your kids. They'll choose your nursing home."
"Cyberspace is so scary I downloaded in my pants."
"When you do a good deed, get a receipt, in case heaven is like the IRS."
"Sometimes I wake up Grumpy. Sometimes I let him sleep." (seen near Walt Disney World)
"As long as there are tests, there WILL be prayer in public schools."
"Change is inevitable, except from a vending machine."
"He's dead, Jim. You grab his tricorder, I'll go for his wallet."
"Very funny, Scotty. Now beam down my clothes."
"We are Microsoft. Resistance Is Futile. You Will Be Assimilated."
"Jack Kevorkian for White House Physician."
"He who laughs last thinks slowest."
"My wife said she'd leave me if I didn't stop fishing and boy am I going to miss her."
"I still miss my ex. But my aim is getting better!"
"Eschew obfuscation." (seen on an English teacher's car)
"Earth First! We'll mine the other planets later."
"I don't have a license to kill. I have a learner's permit."
"Taxation WITH representation isn't so hot, either!"
"Madness takes its toll. Please have exact change."
"If you can read this, I can hit my brakes and sue you!"
"My wife keeps complaining I never listen to her . . . or something like that."
"Sure you can trust the government! Just ask an Indian!"
"Alcohol and calculus don't mix. Never drink and derive."
"If we are what we eat; I'm cheap, fast, and easy."
"Stop repeat offenders. Don't re-elect them!"
"Reality is a crutch for people who can't handle drugs."
"I said 'no' to drugs, but they just wouldn't listen."
"Hang up and drive."
"Ask me about microwaving cats for fun and profit."
"If we aren't supposed to eat animals, why are they made of meat?"
"Lottery: A tax on people who are bad at math."
"Friends help you move. Real friends help you move bodies."
"Five days a week my body is a temple. The other two, it's an amusement park."
"Some people are only alive because it's illegal to shoot them."
"I used to have a handle on life, but it broke."
"Wanted: Meaningful overnight relationship."
"You're just jealous because the voices only talk to ME."
"BEER: It's not just for breakfast anymore."
"I need someone real bad ... Are you real bad?"
"Out of my mind ... Back in five minutes."
"God must love stupid people ... He made SO many of them."
"Where there's a will ... I want to be in it."
"It's lonely at the top, but you eat better."
"Don't drink and drive, you might hit a bump and spill your drink."
"Consciousness: that annoying time between naps."
"It is caffeine alone which sets my mind in motion
It is by the beans of Java that thoughts acquire speed
The hands begin to shake, the shakes become a warning.
It is caffeine alone which sets my mind in motion . . ."