This definitely depends on the job.
For a software engineer - Jarrod Roberson's answer is perfect.
A share trader - I don't know. I'm figuring that any job where memorizing a deck of cards mirrors a skill on the job, this might be a useful peice of information to include. The real trick is to know enough about the nature of the job and the flexibility of your own skill to be able to apply it.
I've often listed skills developed for fun when I could a context. Examples include:
Being a teacher and presenter for hobbies I enjoy lead to me being a better teacher of technical topics at work.
Loving independant academic research on estoteric topics for fun made me a more critical thinker about the difference between research and experimentation, that makes me a better designer of technology.
Learning a dance style from a radically different culture than my own has made me more aware of cultural diversity in the workplace.
I don't usually call any of this out specifically - it's asking a lot to expect a resume reader will manage to make the connection. I do say things like "passionate about learning - both off the job and on", "continuously working on honing communication skills, particularly across cultural boundaries" - particularly when I know that the job in question will involve these sorts of skills.
There is a caveat here - if you work in the performing arts, often putting some really weird stuff on your resume is advisable. I've heard of important, distinguishing skillsets that included being able to:
- own and drive a car (keep in mind, in suburban America almost everyone can do this... but in NYC, very few members of the population drive or have cars)
- speak a foreign language
- fit your entire fist into your mouth
- catch a flying marshmellow in your mouth (a requirement of Blue Man Group)
Certainly you still want to hone yourself down to most likely cases - even though driving and foreign language speaking are not skills in an actor's main training profile, it's easy to see how a particular role might require them. I'd still leave marshmellow catching off until the job description explicitly required it.