Fork in the Road
The Fork in the Road 5K is a little bit trail run, and a little bit gamble. The course follows routes of trails that fork in one direction or the other during the race. Choose correctly and you'll end up covering 5 kilometers, however, choose the "wrong" fork and you'll end up with fun surprises like an extra hill, or more distance (up to an additional 3k worth if you hit a string of bad forks).
This race does have a number of awards, and happens in Woodnewton, Uxbridge; less than an hour outside of the city.