I think you're being satirical, but actually I've always wanted to learn to use an abacus - and I suspect the knowledge would actually be useful in enhancing my understanding of small math operations and making my on-the-fly calculations more accurate. Better isn't always better.

First time I went to China (1991), we visited a department store where we were checked out by someone with a cash register and abacus on their table. They ignored the calculator on the register, and only used its cash drawer while summing our purchases with the abacus.

I have a mechanical watch which is similar.

Good luck with that!