From the site for the Badwater Ultramarathon:
AdventureCORPS, Inc., an event production firm specializing in ultra-endurance and extreme sports events, hosts the Badwater Ultramarathon in July of each year. Recognized globally as "the world's toughest foot race," this legendary event pits up to 90 of the world's toughest athletes—runners, triathletes, adventure racers, and mountaineers—against one another and the elements. Covering 135 miles (217km) non-stop from Death Valley to Mt. Whitney, CA in temperatures up to 130F (55c), it is the most demanding and extreme running race offered anywhere on the planet.
If you think that's hardcore in and of itself, you should check out the rules and time requirements - YES, THERE ARE TIME REQUIREMENTS FOR THIS RACE - so you don't mistake yourself for being badass. The Rules. It's not enough that you finish this bastard of a run, but you must get your happy ass off the course by hour 60, or they'll do it for you.
Not only that, but you're not allowed to merely sign up for the race and show up on the start date. You have to apply for the race and hope you get in. You have to reveal your running resume, so to speak, and there's no guarantee you'll get in. In fact, they only allow 90 competitors per year. Wow.