To commemorate it, Mental Floss put together an infographic of little-known punctuation marks. I’d never heard of any of them. And some are under copyright? I didn’t even know you could copyright punctuation. Some of the public domain ones include:
- Interrobang ‽
- Snark Mark .~
- Rhetorical Question Mark (see image)
These are kind of fun, but I wouldn’t use them except in jest. I don’t think Strunk and White had anything to say about them, and I have a purist streak. But if it suits you, then freely use that Certitude Point.