Easy Unicode Input от Michael Talbot

Most websites do not give you an easy way to type characters that aren't on your keyboard. With this extension you can add any unicode character in the Basic Multilingual Plane (0000–​FFFF) provided that the font you are using supports it. To enter a character use the keyboard shortcut to trigger the extension and then type the 4-digit hexadecimal code for the character you want. The character will then be inserted where your text cursor is.

The keyboard shortcut is Control+' to trigger Unicode input.

Known Issue: Easy Unicode Input does not work properly where an INPUT field type is defined as EMAIL.