Here's one for the word mavens out there ... Mirabilis points us to the Etymologic online game ... here's the official description:

In this etymology game you'll be presented with 10 randomly selected etymology (word origin) or word definition puzzles to solve; in each case the word or phrase is highlighted in bold, and a number of possible answers will be presented. You need to choose the correct answer to score a point for that question. Beware! The false answers will often also seem quite plausible, and some of the true answers are hard to believe, but we have documentation!

It bills itself as the "Toughest Word Game on the Web" and it is quite the challenge!