Enjoy today's open-ended mentalfloss.com Brain Game Think Thursday challenge. And don't be shy with your response!

I've learned a few things over my 45 years, but I've been luckier than most in that my "useless" knowledge has proven quite useful in my job as research editor for mental_floss.

If you had to choose one, what would
be your "pointless" field of expertise?

Please limit yourself to one answer,
and share it with us in the comments below. Thanks!