Long, fat skis are best suited to free skiing or extreme competitions. Most manufacturers now produce an extra wide, super cool big mountain ski that floats through the powder and is incredibly stable at speed. Salomon AK Rocket Freestyle gear Mogul skis are short with a strong middle and softer tip and tail. They love short tight turns and are similar in construction to slalom skis. One piece of advice - avoid using skis that have any metal in their construction as they may bend.
Acro skis are very short skis that are used for spinning and flipping.
Only used with extra long poles. Formally known as 'Ballet Skiing'. Aerial skis are short for manoeuvrability, but strong enough to take the impact. Helmets are a must. Mogul and free skiers sometimes go for softer race boots that give them more freedom of movement as well as easier landings.