A good friend of mine Miya-san (@miya0001) made a simple yet addictive typing game using WordPress functions: WordPress Typing Game.
You can practice typing (especially those underscores and dollar signs…) while getting to know Template Tags, Hooks and Actions.
Once you finish typing 10 functions, you get your score and a list of those you completed with links to Codex.
I’m sure you can beat my score. give it a try.