Multitasking. My wife can read the paper and watch TV and not miss a single plot element. She can do the crossword puzzle and hear everything being said on a radio broadcast. She can be sending emails and following the action on an NBA game at the same time. I, on the other hand…look! A penny!
Also, I have a very poor sense of direction and will almost invariably turn the wrong way.
Three things come to mind:
Names - I’m absolutely terrible at remembering names of people I just met. This is particularly difficult as I work in a sales role and engage with new prospects regularly. You tell me your name and before the handshake is through I can’t recall it.
Math - I’m not terrible but I was never strong at math in high school or college. I did the minimum required to obtain a diploma or degree. Frankly I rarely have a need for it but when it does come up… I’m f-cked.
Basketball - I’m fairly athletic, or used to be until I hit this later stage of middle-age. But the one sport I could never at least not embarrass myself at was basketball. I can’t walk/run and dribble and I can’t shoot. I’m basically just a body out there getting in the way.
MeanJoe
Handwriting. Was so bad at it that never did it for years until I realized one night that I had forgotten how to write cursive.
Guitar, but it wasn’t from lack of talent, I just couldn’t do it. 
Seriously though, one of the times I broke my left arm the bone didn’t heal naturally so there’s a slight infirmity which hinders how I hold the neck. C’est la vie.
Delicate tasks involving small motions with my fingers. HATE ALL OF THOSE DUTIES. OMG, JUST… NO!
Humility. Damn, it’s hard to be humble.
I suck at art. I’m terrible Drawing, painting.
I did ceramics for awhile. I asked my wife to paint them for me. So they’d look nice.
Another person bad at drawing, painting, etc. Can’t draw a circle or straight line at all.
Also bad a singing. But that doesn’t stop me. 
Basketball. Most sports I can fake my way through and probably have some fun playing against my peers. I can throw and catch a football. I can throw, hit, catch a baseball. Play a little tennis for fun.
But anytime I even attempt to shot a basketball through the net I’m horrible. Give me the ball on an empty court by myself and ask me to shoot free throws and layups for 5 minutes and I might make 2 if I’m lucky.
I have great musical ability, even virtuoso ability on one instrument but I can’t for the life of me draw anything, seriously my five year old daughter surpassed my drawing ability when she was four.
I’m good with verbal stuff scored in the top 96% on the SAT but I just suck at math, I mean I guess technically I am tested as average in math but that’s after forcing myself to study doing the same problems 10 or 20 times, that part of my brain has a peanut in it or something, I just don’t understand it and I’m also terrible at doing simple math in my head.
Oh yeah, names. It’s embarrassing. In fact, if I don’t see someone for several weeks or more, I’m likely to forget their name, even though I know them fairly well.
Programming. I excel at maths and sciences but despite repeated attempts, about two weeks into an intro programming course I start to flounder and fumble. I started out wanting to do programming / comp sci, and love the concepts, but totally fail at implementing anything but a simple read/write or single loop and dropped out of more classes than I can count. I passed freakin’ quantum mechanics for Og’s sake, it shouldn’t be that hard!
You and me both, pal. I have never been interested enough in tech to spend time getting familiar with it. Of course, that fuels the reinforcing cycle - the less effort I put in, the more out of touch I get.
When I try to do the same thing I always do - but get a different result, I’m completely befuddled.
I feel so at odds with where the world is going. I see so many things advertised, and I simply have no interest in them - and no clear idea what they are or why so many other people in advertisers’ desirable demographics ARE so interested.
Running - This is a genetic thing that my nephew inherited, and I suspect my mother also had the problem (but running was not on her list of things to do). I can sorta trot along, but any actual speed is just not in my physical capacity. As a child in gym class, I was always tagging along with the really obese kids who could barely job.
Singing/Carrying a Tune - I suppose I am tone deaf, and can’t keep a tempo. I have even had classes with professional singing coaches (not just local, but entertainment industry professionals). They start by saying “Anyone can sing. I can teach you to sing.” I have defeated them all!
Multitasking, especially socially. I hate it when I’m talking to someone and another person says something to me.
Higher maths. Basic geometry and algebra aren’t bad, but start putting in those superscript/subscript variables and my vision goes blurry.
Music. I’m tone deaf. When one of my kids was little she took Suzuki violin. I went to her class once, and the teacher was playing notes that these pre-K kids were identifying. I had no idea of what any of them were.
My father-in-law had perfect pitch, I’m totally opposite.
I’m a really shitty house keeper. If left to my own devices, I clean sporadically, essentially in the kitchen and bathroom, because otherwise gross. I can’t remember the last time i dusted the place - years is not an exaggeration. I’m not bothered by having a mountain of dirty laundry and ignore it. Sometimes I’m tempted to just throw it all out and buy new shit. There are small piles of stuff around - books, my kid’s toys, flyers that need to be recycled.
Fortunately for all involved, Mr. Wonderland is a great house keeper and keeps the place ship shape when he’s home. When he’s away for work it slowly becomes shabby, and then he tidies when he gets home. He does have a much higher bar for tidiness than I do, and when we first starting living together I told him if he wanted the place spic and span, he would have to do it himself.
Golf. I tend to try to swing the club like a baseball bat, and my boobs are just way too big for any sort of good form. Also I find it to be boring.
Dancing. Even the Wedding Slow Dance Of The Living Dead. No coordination from the knees down, that’s me.
I can’t roll my Rs. My siblings and children can continuously, but there’s no hope for me.
Math beyond 6th or 7th grade level
Spatial relations and mechanical ability (once scored in the bottom 3 percent on an aptitude test).
Reading romantic signals or lack thereof (fortunately Ms. P told me straight out she was interested).
When I was in junior high I took guitar lessons. I had to stop because I could not tune the guitar. The instructor would play a note and we were supposed to tune off of that. I could not tell whether I needed to tune higher or lower to match. I could recognize they were different sounds, but I had no idea the relationship between them. I have had people ask me not to sing happy birthday with the group. I thought I was blending in with everyone else, but apparently not.