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 so cool-looking.
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 OMGWTF?!
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.