Three Peaks Challenge
Les is right, so is Uncle.
There is no quitting, but I am still on sabatical.
As I sit here nursing my bum foot - I've been on crutches for a week - I think of all the crazy sports I used to do when I was younger and in better shape.
Of all that, the most difficult and most exciting was the Three Peaks Challenge which I completed in the spring of 1994 while an intern with Friends of the Earth, UK (didn't agree with them politically on most issues, but it was an excellent experience and I have always thought highly of David Brower - epecially as he denied Al Gore his endorsement while on his death bed).
I did it with some folks there as part of a charitable fundraiser - essentially we ascended and descended the highest mountain in Scotland, England and Wales within 24 hours. Its brutal.
If you ever get the chance, I highly recommend it and my goal is to now complete it again within a year.