Probably a “had to be there” thing, but the funniest thing I ever heard was…
“High-beam in the Cop’s eye”
I’m laughing myself to near pants-wetting level right now, 40 years after.
“I’ll be there in five minutes”
“Five clock minutes of five Mom minutes?”
Me: “Can you do this?”
Friend: “I used to could”
mmm
“It’s not the size of your pencil, it’s how big you write your name.”
DJT
I was with a group of friends, walking down a street. Someone drove by in a really loud car, and my friend said, “You can hear how small his dick is.”
From Phil, a coworker from years gone by: I used to know everything till everything changed. The more I thought about that line, the more profound it was!
I don’t recall when or from whom I heard this, but I use it often: Indecision is the key to flexibility.
My cousin, reminiscing about her life as a girl with three brothers, then a woman with a husband and two sons:
“The warmth far outweighed the stink.”
I the small town I live in, the older gentlemen have two or three places they gather for coffee every day. One time I was talking to one of them at the store I work part-time and he said:
“I thought I knew some things but then I went to coffee and found out I didn’t know anything.”
“I only want 2 eggs to cover my feet.”
My friend Dave had been out drinking for several hours,when a mutual friend told him that his girlfriend was looking for him. When asked if he was going to call her, Dave replied, “Nah. I’m already hung, I might as well swing a while.”
Sometimes when my husband and I are drinking, if he says anything particularly shocking which I think would be fun to bring up later, I’ll text it to him so we don’t forget it. Some I don’t want to tell you guys, but a recent one was “Butt-fuckers in the stars”. Neither one of us remembers what that conversation was about.
I don’t know what that is, but I’d love to hear Johnny Cash sing it.
Yippee ki yo, yippee ki yay… 
My brother’s story: his buddy’s car got impounded, and he decided the car wasn’t worth the cost to get it back. But he wanted his stereo, so Brother and Buddy went down to the impound yard. Buddy and a worker at the yard went back and forth about it, with the worker telling him he couldn’t go get the stereo. Buddy finally said “fuck you, I’m getting it,” and marched out into the yard. A few more workers moved to stop him, and one of them grabbed up a big rubber hose. Buddy said “what, is it enema time now?”
My own story: I was with some friends having fun during a lazy summer day. Someone suggested going on a bike ride; one of our friends said that she didn’t feel like doing it, because it had been years since she last rode on a bike, and she was scared she might fall or something.
At that point I said, totally in earnest, very seriously, and with a complete lack of awareness of what exactly I was saying:
“Oh, don’t worry. Riding a bicycle is like riding a bicycle: once you learn you never forget”.
My most memorable - mostly because to this day I can’t believe it occurred.
I was camping with a group of friends and family. We were next to a river in a steep gorge. Waking up, the shade from the canyon walls kept us in the shade, so it was still pretty chilly when we woke. So no one was hurrying to get out of their sleeping bags and get the day going.
As the sun finally peaked over the canyon rim and shined down on our camp, my one friend’s younger sister sat up in her bag and noticed the warmth. She then said the immortal words: “Wow when that sun comes out…it’s like the difference between night and day !”
We still laugh about this to this day.
In high school I had a blonde friend who had some memorably ditzy moments. Her worst was definitely:
Blonde: I don’t like blonde jokes; I don’t get them.
She never lived that one down.
One time when I noticed a really good-looking woman, my buddy said “no matter how good-looking she is, there’s a guy somewhere who’s tired of her shit.”
That’s a pretty famous saying.