I’ve done this in my dreams. I envy all of you quick enough to do it IRL!
I once went to Ypres (Ieper) for their Armistice Day ceremony. The city suffered infamously devastating destruction and death on huge scales during WWI, owing to its position right on the western front, and they still have a daily sounding of the last post from the elaborate war monument at the edge of town.
The ceremony was preceded by a concert of classical and popular tunes from the war days - “Pack up your troubles”, “Song of the Liberation”, etc. Then came the traditional solemn memorial ceremony at the monument. Which, though sizeable, is at a quite cramped streetcorner which was overwhelmed by the assembled crowd - which included a significant number of english-speaking visitors, mainly from Britain. Once the ceremony ended, this huge crowd had little success in dispersing down the narrow streets, and things were moving very slowly. So numerous was the crowd, so tight were the quarters, and so torturous was the path that hardly anyone had any idea what was going on. You could tell that respectful silence had turned into impatient waiting and very, very slow shuffling. I had a train to catch. It was getting dark, and rainy.
I managed to step up on a curb and glance ahead over the gridlocked crowd, still inching forward unevenly. Realising that we weren’t going anywhere quickly, I quipped “Well, you BET it’s a long way to Tipperary like THIS!” A wave of laughter followed, and you could tell that comment had gone some way to defusing the tension.
(For those who don’t get it, “A Long Way to Tipperary” is one of the popular songs from the time of WWI, which had been played at the concert beforehand. The lyrics include a reference to how it’s such a long way, but the singer’s heart is there already, owing to the dwelling there of the ''sweetest girl I know".)
While visiting my grandads grave, someone noticed that a mailbox had been nailed to a tree in the cemetary. When they wondered why out loud, my dad said “It’s the dead letters office.”
In the home-improvement store with Mr. S, waiting . . . and waiting . . . and waiting for him to pick out the perfect length of trim wood for a project. I wandered off several times and came back to find him still sorting.
Finally, on one of my return trips, I met him coming down the aisle, carrying The Piece. “Got it!” he said.
I replied, “Yes, I know, I saw the puff of white smoke.”
He still cites that exchange as a reason why I am the perfect woman. 
Many years ago, my dad was tentatively diagnosed with prostate cancer. I say tentatively because it was initially via a PSA test, and because of scar tissue from an auto accident in his teens, further testing was initially inconclusive. So for months he was flying all over the Eastern Seaboard seeing specialists, and getting second, third, fourth, etc. opinions about what he should do – or if he should do anything at all. It was probably stressing him out more than it would have stressed out most people in the same circumstances because at that time my uncle (by marriage – my dad’s sister’s husband), who had been in the family since Dad was in his early teens, was then in remission for the prostate cancer that eventually killed him.
So at some point during Dad’s months of waffling, I was talking to him about what he was thinking of doing about it, because at some point, didn’t he have to make a decision, even if that decision was to do nothing for now? He acknowledged that yes, it was really hanging over him. My reply: “wait, isn’t it hanging under you?”
(In the end, Dad had surgery and has been fine ever since.)
This one time, Mrs M asks “What’s this football (soccer ball) doing in the flower bed?”
So I say “It’s just looking round”.
Another time, we’re playing D&D, the impoverished 1st-level paladin wants to ride my (1st level druid’s) war dog. And I say “No, I wouldn’t send a knight out on a dog like this”.
Just to prove it doesn’t always work out so well, I was once presented with the set up of the century. Or so I thought.
My wife was catching up with an old friend who was visiting here from her new home in Vienna. The friend was due to return to Austria later in the week. My wife asked, “Which airline are you flying?” To which her friend answered, “Lauda.”
Now I’m sorry, but you could wait a lifetime for a set up like that to come along, so without hesitation I immediately took a swing to hit it out of the park. I replied, “SHE SAID ‘WHICH AIRLINE ARE YOU FLYING?’”
Nothing but crickets. 
I can’t get no respect.
Not too long ago, I was out at a bar with a bunch of my family and some of their friends. My sister-in-law’s mother had died not long before, and Sis happened to mention that some of her mother’s mail that arrived after the funeral included a cancellation notice for her life insurance policy…effective a month later.
“You know insurance companies–they always try to cancel you after a claim.”
(Note: If this seems crass and insensitive…well, yes, it was. But Sis cracked up along with everyone else, so I don’t think I hurt her feelings.)
My sister is the manager of a bank and complained, a few days after Xmas, that someone had dumped their Xmas tree in the bank parking lot and she had to drag it off to the dumpster.
I said “They probably just heard you are the branch manager.”
I laughed reading it. That joke will basically never get old.
Dad, directing a musical theater show, complaining about the chorus: “They can sing all right, but the dancing, even the marching, ye gods! I say start on the LEFT foot for this dance, and three fourths of them start with the RIGHT foot–”
Me, aged 16: “That’s because they have two left feet.”
Two.
The first one, I’ve never told anyone. I was proud of it at the time, but it always seemed TMI, so I’ve kept it to myself. For all I know, everybody has used it, but I found it kind of special.
Back when I was in my teens, the lady I lost my virginity to (my age) and I had been sleeping together for a couple of months. I lived in the dorm, but she had an off-campus apartment (about a block off-campus). Anyway, one evening, after a extremely long love-making session (that involved quite a bit of acrobatics, on both of our parts), I laid their exhausted, and she said to me, “well, how did you like that, hmmm?”. Without missing a beat, I replied “Pretty good. Not bad. I can’t complain. But, actually, everything…” She punched me in the side before I could get the rest out. This would have been the mid-70’s, maybe 5 or 6 years after John Prine’s debut album.
The second one was not nearly as good, but got a perfect stranger to laugh out loud. Sometime in the late 80’s, I had a yellow Lab mix. He loved to ride in my pickup, so I’d take him just about everywhere. I’d leave the windows down and leave him in the truck when I ran errands (I know, I’d get arrested for that today, but back then, it wasn’t anything unusual). Anyway, the truck had a bench seat and the dog would move over to the driver’s seat when I left. He would just lie there until he heard me walk up, at which time he would sit up behind the steering wheel. Well, I come out of the store and he is sitting there faithfully behind the wheel and I say, “move over, Rover, let Jimmy take over”, as I approached the truck. My dog walks across the bench seat and lies down on the passenger side. Some guy walking into the store I came out of sees this and starts laughing, putting his hands on his knees, he is at it so hard. Now, this was a good 20 years after Are You Experienced?, but not quite late enough for the Classic Rock genre to be well defined, so I was a bit surprised he caught the reference. Even more to find it hilarious.
excavating (for a mind)
That had me busting out laughing too. Perfect!
It reminded me of a similar one-liner type crackup I had in a public place with a few strangers. Some guys were walking their Great Dane in the park. On impulse, I marched right up to them and patted the dog on the head, singing:
There is nothing like a Dane!
Nothing in the world
There is nothing you can name
That is anything like a Dane!
I think they were theatre-type fellas because they just fell out laughing.
I was a sophomore in high school, and my family attended a wedding reception. A few college students were seated at our table. One of them said in a mock-serious tone (I forget the context), “Man does not live by bread alone”. I piped up with “He must have peanut butter” (a response I had heard somewhere). Not all that funny, really, but apparently my timing and delivery were just right because it broke up the college students.
Less of a joke, and more just an inappropriate line:
First day of class. College, graphic design. I’m making the students introduce themselves and tell some weird facts about themselves.
So after some fun stories, the last student says “I’m Mandy.” Thinking she might appreciate being taken more seriously, I say “The class list says Amanda. Can I call you that? Besides, then I won’t be tempted to belt out any bad Barry Manilow songs.” She gets huffy, and says “My name. Is. Mandy. My parents named me after that song.”
Now, I could’ve backpedalled and said “Well, it’s a nice song”… but no, without any hesitation I said matter-of-factly:
"Y’know, WE were going to name our daughter after the song she was conceived to, but then we realized BohemianRhapsody wouldn’t fit on any of the school forms".
I was silently sweating it (and imagining repeating my line to the Dean)… until she joined the class in hooting at the weird teacher.
Years ago, the current Doritos campaign was “Crunch all you want. We’ll make more!” with Jay Leno delivering the line.
About that time, New York City was cracking down on counterfeit goods. They had confiscated thousands of fake Rolexes and the like, and had them piled in a 19 foot mound on some street downtown, with a great big street roller standing by to crush them.
This was all part of a news conference to announce their intolerance for such things.
The order was given, and the machinery started crushing all the swag.
My wife looked over her paper and said “Crunch all you want. We’ll make more.”
I guess you had to be there…
These are great!!
My contribution: (I may have posted these elsewhere)
To a teacher who stood in front of class & declared “People, I have stories that would just curl your hair!”, I replied, totally deadpan, “I heard 'em.” (& yes, I have naturally curly hair.)
We had a brand new project manager who, on his first day on the floor is doing the whole meet n’ greet with my supervisors, very polite, very professional. Then he turns to me, the lowly peon, & says " …and what do you do?" I dunno what posessed me, but I smiled brightly at him & said “Why, jist any pore 'ol soul I can, Sugah!” Thank goodness he had a sense of humor!! :eek:
I was chatting with someone about our plans to visit Dragon*Con this year. We got on the topic of when one truly becomes a geek.
Her: Well, you’re not really a geek; it’s not like you speak Elfish or something.
Me: *Elvish!
*
The best thing about it was I realized it was a punchline, but I also genuinely felt the correction needed to be made, having just read about Tolkein’s fury at having editors change “Elven” to “elfin.”
I was in an email conversation with our college President (with whom I always a cordial, but cool relationship). We both came up with the same approach to deal with a new campus initiative.
He wrote to me: “Great minds think alike”
I responded with: “And fools rarely differ.”
Happily, he found it funny. I shamelessly stole the line from my 8 year old daughter (at the time) but used to good effect, I think. I’m not sure where she heard it or if she made it up herself.
I saw an aquaintence on a shuttle bus this morning. She was just coming out of a nap. We had a short discussion about how bus naps are the best naps ever. I mentioned that I want to get a bus installed in my apartment so I can have better naps.
OK, not funny, but she laughed.