Punctuation marks are symbols that indicate the structure and organization of written language, as well as intonation and pauses to be observed when reading aloud. In written English, punctuation is vital to disambiguate the meaning of sentences. The rules of punctuation vary with language, location, register and time and are constantly evolving. Here are some forgotten punctuation marks which should be remembered.
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.
Also called a Wedge, an Up-Arrow, and a Hat, which is cute. The word is Latin for "it lacks," which is convenient, because the caret is primarily used to indicate something that's missing from the original text.
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.
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 means "Little Williams," which is interesting but unhelpful. They're named after a 16th Century French printer. Their primary role is in non-English languages that use them as quotation marks.