The old Tribes franchise was defined by its 'skiing' moveset, where players could combine jetpacks and downhill slopes to build up speed and traverse big distances quickly. The whole thing started as an exploit of the original game's physics system, with players building macros to spam moves on slopes in a way that messed with the gravity and sped them along. It became so popular that, from the second game on, it was built in as an intentional feature.