Ron Weasley Christmas Sweater, Sorcerer's Stone

During Harry's first Christmas at Hogwarts, we're introduced to the Weasley Chirstmas sweater, a tradition of Molly's. Each of her children receives a tweedy sweater with their first initial on it each year. Above you can see Ron's sweater, dark red with a gold R.

Many patterns have been written for this sweater, so I've included a few below.

The Weasley Sweater, from Charmed Knits
Harry Potter Sweater, from Rowan Pride and Joy: Harry Potter
The Original Harry Potter Sweater (this one claims to be the actual pattern used for the sweaters in the movie!)