It's not particularly useless, but like, I don't use them enough (or at all in the second) to recall them so perfectly.
Also, they can only be inherited from the mother.
...And they were once an organism of their own?
I should be studying this instead of sharing it on the internet. 
I remember e = 2.7182818284590
btw. Not useless for me, but I also remember about 4000 songs from my playlists (and theirs name too), also about name of 8000 comics and novels (ofc, some of them I need to think about few seconds),... and also I remember nearly all mobile numbers from my phone. (I even know my moms identification number (because I always needed it when I wanted to report some problem with Internet to my ISP)
I know so much... So much about moths. I love them. 
...it also has nothing to do with my career. (art history/Egyptology)
I know a lot of stuff that seems pretty useless but a surprising amount of things I thought were useless actually became useful at some time (though some of those times were really short).
Things I haven't found any use for is for example that the a rabbits chewing circle is controlled by 3 groups of muscles instead of two as was previously thought or that some molluscs actually swim by curling forward and backwards instead of sideways like the rest.
I don't have another tiny animal to mention, but here's something obscure!
You won't find it often in music but there's an audio-based illusion that exists called the Shepherd Tone. It's basically a constant rising or descending pitch of a single note, though the effect can be achieved through a chord and/or a series of notes as well.
It works through two layers where one can disguise the fading in and out of the low and high notes in a loop. However, it works better with an additional third layer that masks the transition even more on both ends. If you're willing to pay attention, you can start to find the beginning and the end of the loop of most instances of it being used. The second example below makes the loop much easier to hear and underatand since it seperates the layers by panning them on the left and right.
I'd argue the most famous example of it is in a Mario game and it sounds like anxiety bc of the eerie chords behind it.
My favorite example of it is here in a more band-focused setting. La Dispute's "Fulton Street I" features the illusion by having a guitar play a series of notes constantly going up the neck. The moment's at around 4:19 if you wanna skip there.
It isn't totally useless, but I constantly wonder how much better my foreign language abilities would be if I replaced the pokemon part of my brain with like, Spanish grammar. Type matchups are at least helpful when my roommate asks pokemon go questions, but pokemon lore? Wish I could replace that with irregular verb conjugations...
Wait. Does Spanish have irregular verbs? I never thought of it before.
Edit: Welp. After a quick search, I discovered that yes, Spanish does have irregular verbs.
If it makes you feel better, I didn't even know which verbs were irregular in my own language.
Irregular verbs are the bane of my existence. I thought I could escape from them outside English, but alas... they surround me. And when I though I was free in Mandarin, the tones came for me instead.
In the Patrick Troughton era of Doctor Who (before homosexuality was legalized in the UK), Troughton would deliberately hold hands with his male companion to annoy a homophobic executive.
This is why Patrick Troughton is my favourite classic Doctor.
This.
She technically should be unable to get drunk or enjoy alcohol at all, since she automatically purifies liquid that come into contact with her into pure water.
lol you'd think but no. It was during WW2 iirc something about diverting a river from the lake to one of their industrial areas. And the lake happens to get like no rainfall, and became super salinated and toxic fish. It's now entirely dried up basically with like 8 residents refusing to leave. Poisoned by eating the fish of course.
The color of the egg a chicken lays is determined by the color of its earlobes
I know a lot of useless sh
t about chickens. I have no chickens.
This collab from defunctland and yesterworld about the journey into imagination ride has been occupying my brain rent-free for like a year
Yan an road and Xujiahui road in Shanghai used to be rivers... they used to delimit the French and international settlements before. Chinese filled them and made huge motorways to get in and out of city center. Completely useless, but now some obscure location names make sense (like Xie bridge on xujiahui road even though there obviously no bridge... but zebra crossing...)
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