Tool: Layers, game design cards
Layers is a deck of brainstorming cards specifically geared towards video game design, considering not only mechanics or emotions, but also technical features such as controllers. The Layers cards could be used both for inspiration and as a guide for analyzing the abstract components of games. During the design process, the cards are arranges in six different layers, each one representing an aspect of the game and in direct relationship with the others.
Download the Layers cards at http://www.layersdesigntool.com/
See also the IDEO cards and the PLEX deck