Warg

Wargs are people with the ability to enter the minds of animals and perceive the world through their senses and even control their actions.

Known Wargs

 * Orell, a wildling
 * Bran Stark

In the books
In the A Song of Ice and Fire books a "skinchanger" is a person with the ability to enter the mind of an animal and control its actions and perceive the world through their eyes. A "warg" is a skinchanger that does so with wolves.