Flashing D20: 2010 - ThinkGeek
This was an idea which came from one of our D&D obsessed merchants. It's a pretty simple idea - just a 20 sided die that flashes in celebration when you roll a 20. Inside the translucent plastic body is a tilt switch, battery & LED. I was worried that the mechanical action of the tilt switch would effect the randomness of the outcome, but after doing a statistical analysis of more than 100 rolls & consulting the office statistics guru, we decided that any error introduced was trivial for most casual gamers. On this project I also did the packaging template design so that the lights would not come on by accident while sitting on a flat surface. In order to make it at the correct price-point, we couldn't have replaceable batteries or a pull-tab separating the contacts before purchase.

Critical Hit LED d20 Die - $9.99