In the project I am currently working on everything is based around the essence of "interests". One of the most important and bold UI elements in this project, is a button that when pressed gives us the feedback of "I found this really really interesting".
We would like to prototype/standarize a pictogram (an icon actually) to indicate that positive feedback and we would like to stay away from a star, a heart or a thumbs up button. On hover the button will display a tooltip with a text like "I find this interesting" just to make it clear for not accustomed users but nevertheless the user should eventually train himself to understand the interesting button wherever he sees it.
What would you suggest?