Special Characters

What’s the best way to add my own item to the to the post toolbar? I couldn’t make my way through the Tiny MCE documentation to edit their tool. Maybe it’s easier to just add 12 new items to the existing toolbar items?

Specifically, I have 12 special characters I’d like create buttons for. I want my users to be able to click the toolbar button and insert a special character/html entity. I’m not aware of any best practice for doing so. Any help is greatly appreciated.