Steal this idea: Alan Turing 5k
I just finished reading Logicomix, a good graphic novel about Bertrand Russell (the man who attempted to prove that 1+1=2). It's a bit over 300 pages long but the most interesting part was a note in the index that Alan Turing was "an accomplished long-distance runner." You don't hear very much about this aspect of Turing, and yet to accomplish his world-class Marathon record, he must have spent a significant part of his life running.
This gives me an idea, which I hope someone will develop into a reality: an Alan Turing-themed 5k. There are already events where you race a bear, escape from zombies, and follow clues Amazing Race-style to find your next checkpoint. So why not a run with challenges based on math, logic, and cryptography? I can see the race shirts now: "I passed the Turing Test!" C'mon, somebody, make this happen!