Duncan Adams' trademark move is the zero spin -- or switch straight air. “"To go big on a zero air, like Duncan Adams, is crazy," says fellow skier Gus Kenworthy. "It’'s completely blind from the switch takeoff to the switch landing and he'’s landing high up on the wall."

Noah Bowman learned a switch alley-oop double 900 just days before X Games Aspen in 2012. He earned a silver medal thanks in part to the trick, which is among the toughest done by skiers in the halfpipe today.

The double cork 1080 has become routine these days, but when you add a true tail grab, as Kevin Rolland did at X Games Aspen this year, the difficulty spikes.

Justin Dorey's pipe runs often include some of the most difficult tricks ever attempted. He has landed unnatural double alley-oop flat 9s in practice but never in competition. And at X Games Aspen 2012, he crashed and injured his shoulder attempting a switch double cork 1080.

Henrik Harlaut is the only skier throwing throwing nose-butter double corks in slopestyle contests and he won X Games Aspen Big Air with a never-been-done-before nose-butter triple.

Triple-cork variations are still rare, but more skiers are landing them now. The first triples in skiing at an X Games contest took place in January in the Big Air finals. Gus Kenworthy, who was the first to land a switch triple 1440, was among the Big Air finalists.

The flatspin is one of skiing'’s most stylish tricks, but even after Bobby Brown introduced the triple flatspin in 2010, the fact that it still hasn'’t caught on speaks to its difficulty.

The switch double misty 1440 is still regarded as one of freeskiing's most technical spins and axes. Kai Mahler has added a double Japan grab to the move.

Tom Wallisch, the recently crowned FIS world champion in slopestyle, has many difficult tricks up his sleeve, including an unnatural rodeo 1080 and a switch unnatural 1440, which he first landed three years ago during X Games Big Air. "No one has done it since," Bobby Brown said.