Night-ski the Tetons.
With a wide variety of terrain and plenty of vertical - easily reached via car and a short hike - Teton Pass is Jackson's most popular backcountry playground. At night, under a full moon, it becomes a Jedi challenge. You can't see. You can't hear. The key is to choose your line well (read: no trees) then commit to it. Glory Bowl and Shiver's Ridge are the best runs, with easy hiking access from the parking area on top of the pass (leave a car near the bottom, since night-hitching sucks). With two headlamps you can avoid smacking into obstacles, but the real skill is feeling the terrain under your feet and reacting to it. Practice by skiing groomers with your eyes (briefly) closed. Hit the Stagecoach Bar at the bottom of the pass, either after or before.