Because Tully2001 is no longer, I decided to make a new one. It will be incomplete at first, but hopefully you can help ;)

Basics:

Italic
_Italic_ or *Italic*
Bold
__Bold__ or **Bold**
Bold Italic
___Bold Italic___ or ***Bold Italic***

Code quotes
"Code quotes" with 1 in front and 1 in the back

Sectional breaks (see top)
3x underscore in a row

Headers:

Header 1

#Header 1

Header 2

##Header 2
etc.