I have a quiz-based application where users can leaf between questions and select answers. When they're done, there's a "done" button they click.
I don't really have polished graphics skills, so I may be additionally limited to using one of these: http://www.iconfinder.com/search/?q=iconset%3Aorb or trying to photoshop my own version of one of them.
But really, that's a side point; I'm more interested in a graphical symbol for done. I don't want a button that says "done" :)
Also, I'm okay with a semi-intuitive symbol, because I will confirm with the user that they're really done and not going to change their mind.
Edit: Thanks for all the great feedback. Here's the updated image post-UX-question: