Have a look and see how many of them you knew about previously. I knew 8 of them before reading the article. A few I wasn't familiar with are:
The exclamation comma, for when you are excited, but also not finished.
Also, the asterism, for indicating minor breaks in a text, or to mean "untitled," which is great since "untitled" is a title, but maybe an asterism isn't.
There's also the because sign, which is the flipside of the therefore sign, and I love that, just because!
And finally, the aptly named snark:
Enjoy all the punctuation you can, that's my motto!