Why don't we use these punctuation marks more often?

Dagger

Also called an Obelisk. This bad boy (on the left), and its two-headed friend (on the right) the Double Dagger or Diesis, represents a javelin, which is cutting out extraneous stuff from your text. Its primary use through the ages has been to mark out superfluous repetitions in translation, though nowadays it mostly just stands in as a kind of footnote.

Solidus

Not to be confused with a slash! The Solidus is also called a Shilling Mark (presumably by old British dudes in top hats) and it is at a much steeper angle than a boring old backslash. Back before decimilization took the world by storm, the Solidus was used to set apart different values of currency from each other.

Asterism

The Asterism has an awesome name, a cool look, and a really lame usage. It’s for indicating minor breaks in text. It can also mean “untitled,” apparently.

Guillemets

Guillemets means “Little Williams,” which is interesting but unhelpful. They’re named after a 16th Century French printer. Their primary role is in some languages that use them as quotation marks.

Sheffer Stroke

Mainly used for Boolean functions and propositional calculus. Truth tables. Stuff like that.

Because Sign

This one’s so cool. It’s like the “Therefore” sign, but upside-down, and it means because.

Exclamation Comma

Just because you’re excited about something doesn’t mean you have to end the sentence.

Question Comma

The interrogative version of its best friend the Exclamation Comma.

Interrobang

It’s a combo-Exclamation/Question mark, and it’s awesome. It is the glorious punctuational equivalent of saying OMGWTFBBQ?!

Caret

Also called a Wedge, an Up-Arrow, and a Hat, which is cute. The word caret is Latin for “it lacks,” which is convenient, because the caret is primarily used to indicate something that’s missing from the original text.

Section Sign

To indicate sections in a text, mostly by lawyers, who are too good for regular punctuation marks. You probably knew this one, but it’s cool-looking, so.

Hedera

Hedera is Latin for ivy. Why that is relevant here is not very clear at all, but this little glyph was used back in the day to mark paragraph breaks. Seems like it was probably really hard and annoying to draw, but it looks nice.

Pilcrow

This one’s also for paragraph breaks. Most people will be familiar with it, though not with the fact that it’s called a Pilcrow. It’s also referred to as “The Blind P,” which sounds like a good name for some hopelessly twee indie band. “Pilcrow” is the Middle English word for “Paragraph.” You will never be able to use that fun fact in real life.

Snark

Also called the Percontation Point and the Irony Mark, this one’s used to indicate that there’s another layer of meaning in a sentence. Usually a sarcastic or ironic one. So it is essentially a tool for smart people to use to make stupid people feel even stupider. Which makes it the best punctuation mark of all.