Since there is a lot of dice chat on here right now, I though I'd bring up some possible modifier dice. These are rolled to modify the result of another roll, for example a reaction roll. There are other designs for such things out there, but I didn't find ones quite like these that I am proposing. You can view a plan for the dice here -
http://shadekeep.com/files/modifier_dice.png
Basically you roll the top die, and if you get the square-with-a-plus symbol, then roll the lower die. This should mean that most of the time modifiers will be modest, but occasionally much more significant.
Not sure how much utility value these have, but figured I put 'em out there.