The mnemonic for resistor color codes. BBROYGBVGWGSN
Nearly thirty years ago when I was a high school senior, we had to memorize and recite the introduction to the Canterbury Tales in our English Literature class. In middle English.
Whan that Aprill with his shoures soote
The droghte of March hath perced to the roote,
And bathed every veyne in swich licour
Of which vertu engendred is the flour;
Whan Zephirus eek with his sweete breeth
Inspired hath in every holt and heeth
The tendre croppes, and the yonge sonne
This isn’t the whole introduction of course, my memory is finally starting to fade a bit, but I just looked it up, and it wouldn’t take me long to get up to speed and recite it in whole once more.
Other useless things I remember:
The names of almost all the GI Joe characters from 1982-1985.
The names of almost all the Transformers from 1982-1985.
Many of the things already listed, and…
Crossword puzzles kept making me look up the NATO phonetic alphabet, so I memorized that. For a while. I can’t always dust it off when I have to spell something on the phone.
I know truckloads of useless, trivial information. I’m 73 now, and Jeopardy shows me a few times a week that some of it has disappeared. “I used to know that!”
Sarah Cynthia Sylvia Stout
A few days ago, my brother and I tried to name players of some of the football teams that played at the 1982 World Cup. We managed to come up with about 8-10 names per team most of which we both remembered over 40 years later.
I think I can still do this. I served 1980-1993 so it’s been awhile. From memory: To quit my post only when properly relieved.
I think that’s right.
Take
Walk
Report
Repeat
Quit
Receive
Talk
Give
Call
Salute
Be
Those should be the 11 starter words for the general orders. Something like that, IIRC.
I looked it up and it is correct. I remembered all 11. Not bad after 43 years. On 4/25 it’ll be my 43rd anniversary since graduating boot camp in 1980.
My memory isn’t as bad as my wife would like to think! 
I unintentionally memorized the Cap’n Crunch Sea Shanty song sometime back in the early 1960’s without realizing it. It lay dormant in my brain until recently when during a family vacation where we discussed our favorite sea shanties, I broke out into that song.
I definitely both impressed and frightened my grown children.
Cap'n Crunch 1960's Sing Along - YouTubeCap’n Crunch sea shanty
At church camp when I was a pre-teen, we studied missionary work in China and the only thing I remember about that is learning to count to 10. I just put the words in google (phonetically) and found out it is Cantonese. Why the hell do I remember that more than 55 years later?
I had to memorize some Shakespeare sections in school (“All the world’s a stage…”) So did my wife.
I was the last generation of altar boys that had to memorize the Mass in Latin. I’m kinda rusty on that. Had to memorize all those catechism questions and answers, too.
I’ve been in a few plays, and had my parts fully committed to memory.
Oddly, what really sticks in my mind are absurd things that I didn’t even try to memorize. Parody poems in Mad magazine (“I think that I shall never hear/A raven whose is more sincere…”), Poems from Bored of the Rings (“A king of elves there was of old/ Saranwrap by name…”), and the first stanza from Jabberwocky (“'Twas brillig and the slthy toves/ did gyre and gimble in the wabe…”) . The definition of a kiss that appeared in Ripley’s Believe it or Not (“An anatomical juxtaposition of two orbicularis oris muscles in a state of contraction.”) and random numbers (14,622,047,999 – it’s claim to fame is that if you divide it by 10, the remainder in 9; if by nine, the remainder is eight. Et cetera. Also from Ripley’s)
It ended with “And so a George was reinstated.” I’ve updated it with “Bessie and Charlie to end the list, / And that’s the lot – not one’s been missed.” (Well, Maude and Jane, maybe…)
Something useless I deliberately lodged in my brain in high school twenty plus years ago.
Parrot. Record. Swimming pool.
Why? As a mnemonic for PVC (polyvinyl chloride). But I never needed the mnemonic, it was a silly thing to use a mnemonic with and now it will never leave me. I should put it on my tombstone so future generations can suffer as I have.
James James Morrison Morrison Weatherby George Dupree
I have the rubber ducky song from Sesame Street memorized. Both verses. Many years ago I impressed a coworker with that, and now she is my wife.
One never knows…
Albermarle, Butterworth, Chesapeake, Davenport, Ellefant, Fessiden, Garrison. A series of streets in NW Washington DC. Unintentionally.
The list is from memory, and I realize I’m not sure of some of the spellings. Which is odd, because it’s usually pronunciations I’m not sure of.
The first Sura of the Quran in Arabic.
My crush’s phone number from the 10th high school reunion in 1974.when they printed such information in the brochure. She lived far away and I never saw her after high school but her phone was 254-1964. I lived near Route 254 and 1964 was our year of graduation.
Stallone’s speech at the end of “Rambo, First Blood”. “Want?!! I want what they want…”
Actually “Rambo, First Blood Part II”
Col Trautman, “What do you want, John?”
Rambo, “I want, what they want, and every other guy who came over here and spilled his guts and gave everything he had, wants! For our country to love us as much as we love it! That’s what I want!”
Col Trautman, “Good luck, John”
Someone mentioned their first school locker combination. Mine was 13-37-6. I have no clue on other ones.
The theme song to Gilligan’s Island
The only two phone numbers I know that aren’t my number are 867-5309 and a sort of friend when I was growing up. I don’t know the phone numbers of friends that were closer, I don’t know why i remember the one and not the others.
I can still remember my student id number from high school – 98095. I graduated in 1998.
I remember my childhood phone number, but I can’t remember any other phone number I had between then and now.
When I was younger I had pretty much all the dialog from Month Python and the Holy Grail memorized, but I’ve forgotten most of it by now.