Something else. I've always wanted a pilot's license, and flying a single-engine around the world would be awesome. And since we're talking unrealistic-things-that-won't-happen, I'd like it even better if I was flying with a few pilot buddies so we could take turns flying/drinking.
I hiked the Appalachian Trail in 2009, it was by far the coolest thing I have ever done in my life. I did it right after separating from the Marine Corps, I had the money and I had an intense desire to not work. It was an amazing experience filled with beautiful views, wildlife, all sorts of odd characters, plenty of herb, crappy trail food, disdain for objects of nature(rocks, roots, flat land) and some really bad weather. There were quite a few times I wanted to call it quits and head home but after spending a day or two in town pigging out(the amount of food you can eat when you're burning roughly 5-6000 calories a day is ridiculous) and guzzling beer I was ready for the trail again. After finally reaching the northern terminus of the AT at the top Mount Katahdin it was worth every step I took. I voted for walking of course. Currently planning my next hiking adventure on the Pacific Crest Trail.