Thanks to the thread about Jim Wampler's Mutant Crawl Classics, I learned about this man who makes specialty dice. That die pictured? That's one of his emoticon dice. The picture is from his website.
I just asked about ordering several of them. Here's why:
In Dungeon Crawl Classics, normal ability modifiers range from -3 to +3. If you have an encounter where you need a reaction roll, and no Personality modifier is involved, roll one of these dice. If there is a Personality modifier involved, roll one die per point of modifier. If the modifier is a penalty, select the worst result. If the modifier is a bonus, select the best result. Instant reaction rolls!
If you need a reaction for the party as a whole, determine the total modifier and then roll that many dice (or one die, if the total modifier is +/-0.
Plus, the emoticons are easy to read. The images here are also from the dice webpage.
It is pretty easy to see how you can make modifiers by adding or subtracting dice to determine reaction as well.
(Of course, this is really all about wanting cool new dice.)