Dipsea.

In the June 2010 edition of Runner's World Magazine, they have an article about a race titled -- "Tough Love". After reading about this race, that title is very accurate!

From the website:

"First run in 1905, the Dipsea is the oldest trail race in America. It is run every year on the second Sunday in June. The scenic 7.4 mile course from Mill Valley to Stinson Beach is considered to be one of the most beautiful courses in the world. The stairs and steep trails make it a grueling and treacherous race. And its unique handicapping system has made winners of men and women of all ages. Because of its beauty and challenge, it is a very popular event, and because of safety and environmental concerns the number of runners is limited to about 1,500. While racers enter from all over the world, the Dipsea is primarily a Northern California event and the entry process is tilted slightly to favor local contestants. Please see the section on How To Enter for details."

Read the "how to enter" portion. It is wild!! You basically have to beg and/or bribe your way in. I like it! ;)