I wonder what else I could fit in my brain...

I coached high school cheerleading for right around 7 years. A couple years ago that chapter of my life ended.  Before I coached, I was a high school cheerleader for 4 years. That is 11 years of learning everything about cheerleading. Basically, I learned as much as I could about a whole world of high school girls, dance music, night games, bus rides and crazy parents. Now that I am done coaching (most likely forever) I am realizing my brain is full of (now) useless knowledge.
For example:

This picture shows 4 stunt groups doing a paper doll. (there are probably a group on either side of the picture as well.) The two on the end are assisted partner stunts (BTW those girls are beasts with great form!) This stunt is illegal in Oregon high schools because the fliers are in extended one legged stunts, and are touching the fliers next to them who are also in extended one legged stunts. The side two stunt groups are also illegal because they need a non-weight bearing spot behind the stunt. The coach didn't know what to do with the girl in the back so they made her stand there randomly. (she should be spotting one of those partner groups.) The base in the third group should have her legs locked out so that the stunt is more stable.

See what I mean? That was useless to all of you. And I could have kept going. Sure I have used some of my coaching knowledge since I left the sport (I have taught Zumba and I choreographed a flash mob) but there is a ton of stuff that is taking up space in my brain.

Other useless things that are taking up important space in my brain:
Algebra

The other day I subbed a period of  6th grade math class and they were working on problems like this. I kind of remembered how to do it, but seriously, I have never needed anything like this in real life. (I have used regular math, percentages and fractions in regular life, but I still haven't had to solve for X).

Overhead Projectors

In my teaching program, we had to learn how to use one of these dumb things. Like we seriously had days and weeks worth of lessons on this ancient piece of technology. These are pretty much obsolete now.

Wrestling Stats

I scored wrestling in high school and I have done it a couple times since. But now wrestling has been cut from middle school, so there isn't much of a need for this skill of mine. But I still know take downs and reversals are worth 2 points, near falls are 2 or 3 and an escape is worth 1.

What is taking up space in your brain?