Guitar sounds fun

Deduction, at superhuman speed of course just like neos kung fu speed.
Deduce the optimal stock market traction to gain a big chunk of capital so I can than deduce the best proper services to provide, or find the proper projects

I did Brazilian Jiu Jitsu for a while untill after the 3rd injury I realised this isn't going to be good on the long run and I stopped doing it. However, it was long enough to see what a magical power that is so I'd say that being able to posses the skills of a black belt without going thru the training would be quite nice.

People don't realise how helpless you'll feel trying to wrestle with someone who knows what they're doing. Being bigger and stronger will not save you unless you get really lucky.

Psychology.

I assume psychology is very useful for social interaction, but complicated and mid-impact enough that I personally wouldn't bother to analog-learn it.

maths.

I never had enough brains to not suck at maths.

Playing the piano, or just singing at a professional level. Would be amazing to know, but takes years of constant practice and teaching to learn.

Whatever skills would result in what the deep mediators to control autonomic functions like heartrate and could mimic death. I don't just want the control thing though I want the whole kit that comes with it which would likely have some martial arts. figure like and ideal shaolin type of thing.

Math, so so much math...

Medicine. If I could get an upload to make me an instant doctor, that would be amazing.

C2-niveau francais, s'il vous plait.

edit or as translate google would put it: niveau C2 de francais, merci.

the ability to think calmly and rationally

I would immediately download more RAM. No hax. Really works.

Being able to feel joy/happiness. I really don't understand or know what those things are but everyone says it's wonderful and awesome. So It would be awesome to experience it at least once.

Knowing every tree, plant, insect, ...

How to fluently speak a foreign language. I'm A2 with French but I could live with Spanish or German as well.

Ability to play the guitar like Gilmour, EVH, Page and Hendrix.

If I had that technology, I would upload everything available on file. The common fictional notion that you could "fill up" your brain is wrong.