Weasley's Ford Angela

The Weasley's Ford Angela is a car that was owned by the Weasley's.

Harry's escape
Ron, Fred, and George took the car in order to break Harry out of the dursley's house to which they almost fail, then they take the car back to The Burrow.

Drive to Hogwarts
Platform 9¾ was sealed off from Harry, and Ron, so they couldn't get to Hogwarts, so they took the car to get there. They weren't allowed to be seen, so they put the invisibility booster in use turning the car invisible. Later the invisibility booster runs out, and the needed to find the train, then they found it, and they were forced to take off, and leave the train (Harry had almost fallen to his death along the way). They encountered the Whomping Willow and they barely escaped. In anger, the car tossed them out, their belonging, and their pets, and left them.

Forbidden Forest
After their rough encounter with the spiders the car roars out of nowhere, and saves them from the spiders. Ron is almost eaten by a spider until Harry uses Arania Exumai on the spider. Then an army of spiders come, and they are forced to fly away, and they leave the car, and it returns to the forest.

Trivia

 * In the video game the Whomping Willow uses the Weasley's Ford Angela as a projectile when you fight it.