A twister is usually formed when strong thunderstorms mix with heavy wind and form a funnel-like shape. From here, the twister usually sucks up anything in its path, including debris, and is usually very deadly. It does not have to touch the ground to be considered a twister, but a tornado's wind speeds are at their highest when it does.
In video games, the use of twisters varies from harmful to helpful. Sometimes the player can use it to advance or as a weapon against enemies, while in other games it is in the environment.
As a Level Mechanic
Twisters of this type are often smaller and used either as a levitating device or a way to cross across long chasms.
In Mario & Luigi: Superstar Saga, the duo use twisters to extend their spin jump. In Klonoa, Klonoa uses tornadoes to reach higher platforms, a mechanic also repeated in Super Mario Galaxy.
As a Weapon
In this category, tornadoes are used as elemental attacks, usually lifting the enemy in the air and doing damage or trapping them in a vortex. In Bioshock, the Cyclone Trap plasmid throws enemies into the air when they step on the twister trap, causing damage when they fall back to the ground. In Mega Man 9, Tornado Man throws twisters to attack Mega Man. Fujin in Mortal Kombat: Armageddon lifts opponents into the air with his wind, without the need of a weapon.
One of the final powers you unlock in Infamous 2 is the Ionic Vortex, in which Cole gathers up a huge amount of energy and hurls a electrically charged twister out in front of him, destroying and flinging around anything in its path. In The Legend of Zelda: Twilight Princess, the Gale Boomerang can be used to summon a small twister and pull items & enemies towards the player.
Cyclones under this group usually look the most violent and can have an impact on gameplay. Used this way, they symbolize chaos in the world. In The Legend of Zelda: The Wind Waker, tornadoes in the ocean can fling Link and his boat around, changing wind direction. In Alan Wake, a twister represents the final confrontation in his nightmarish scenario, throwing everything from school buses to small cars at Wake. In Superman Returns, the final boss in the game is a tornado hovering near Metropolis. In FUEL, tornadoes would occur randomly and also be triggered by race events.