Inspired byWhat’s the most obscure thing you know?.
For me, it’s a tossup:
This is hard to describe, I lay on my stomach, bend my knees, then swivel my legs around and put my left foot in my left armpit and my right foot in my right armpit. 
Beating Super Castlevania 4 on SNES without dying.
Remembering where all the secrets were in Legend of Zelda, over a decade since I first played it. 
This might be a very marketable talent in some elements of the film industry.
Which reminds me of another of mine- voluntarily flaring my nostrils.
I do an eerily accurate impersonation of the coroner munchkin from the Wizard of Oz.
I too can flare my nostrils on cue - runs in the family actually.
And I when I was a kid I could turn my belly button inside-out.
I can do old-english style calligraphy lettering
Translate Latin into a broken and stumbling form of English
and back in the day I could roll the best joint on the block…
hillbilly queen–as soon as I read your post, I couldn’t help it, I immediately thought of this. Perhaps your problem is that your husband is simply intimidated by your expertise!
Just joshin’ ya–you knew that right?
bella–also a nostril flarer
I can crack my jaw at will, make armpit noises, and write quickly and flawlessly in Germanic runes (used to write all my notes in them … really confused the one high school teacher who decided to collect our notes).
Actually, I learn all alphabets with incredible speed. I just forget them if I don’t use them much, which is why my Cyrillic, Greek, Braille, Ogham, Hieroglyphics, Heiratic, ASL fingerspelling and Druidic handspelling are a bit rusty. 
I can do reasonably good xoomei overtone singing.
I can throw a peanut M&M as high as you like (my daughter likes it if I hurl it as hard as I can), and catch it in my mouth.
I’m such a hypocrite. I mentally “tut-tut” these goofy Mostly Purile Sh-, er, Mundane Pointless Stuff topics as being, like, so totally non-intellectual, dude, y’know? So why do I enjoy posting to some of them so much?
I can write backwards with my left hand. (I am left handed.)
I can…put my fist in my mouth.
I can put both my legs behind my head.
Those are pretty darn useless.
I can crack virtually any joint in my body voluntarily, including: neck, back, hips, ankles, knees, wrists, elbows, and jaw. Interestingly enough, my fingers are harder to crack than these.
I, too, can flare my nostrils (and wiggle my ears).
I can say the “Betty Botter” tongue twister error free several times in a row (and very quickly). There’s actually a tape of me, somewhere, on that short-lived TV show America’s Funniest People reciting it.
I can recite all Kentucky Derby winners from 1970-present, in order, and in most cases can also name owner, trainer, jockey, and/or pedigree. I’d say that’s that most useless of my skills.
One-handed cartwheels.
Remember 4-sided dice? Those funky 1-side-shy-of-a-pyramid dice that were used in D&D?
I could spin them like a top. Every time.
Still can. 
I can still remember how to sing the fifty states in alphabetical order. Anyone else recall “Fifty Nifty United States”, from junior high chorus class?
It’s been a while, but I used to be able to do this. Maybe I’ll have to practice.
My talent? I can remember obscure details about a situation years later. Just so you’re not jealous, I never know what day of the week it is.
And I used to be able to play Nintendo with my feet.
…except i don’t know how!
i can also wiggle my eyeballs rapidly and it makes people absolutly freak out!
i would put down my dart throwing ability, but it actually makes me a bunch of money/beer in bars, so i guess it ain’t so useless!
– I can play tetherball like a BOOH.
– I can touch my nose with my tongue. Of course thats not TOTALLY useless, but considering my present social situation… 
I can touch my nose with my tongue.
I can do an extremely loud, scary and realistic imitation of a dog barking.
I can balance things.
I realize sometimes there’s a fine line between fora, but I would think this is also an opinion poll so I’m going to move it to IMHO.