Gamasutra - Evaluating Game Mechanics For Depth
Former Insomniac designer Mike Stout takes shares a useful rubric for judging the depth of play mechanics, including checks for redundant ones, in this in-depth design article, which contains examples from the Ratchet & Clank series.
Game designer Mike Stout discusses how to build game mechanics with enough depth to stay interesting: tie them to varied and meaningful use of skills.