Arys Oakheart

Arys Oakheart is a background character in Game of Thrones. He is played by an unidentified extra. He is a member of the Kingsguard and defends King Joffrey Baratheon as he defended King Robert Baratheon before him.

Season 1
Ser Arys was among the guards that attacked Eddard Stark when he tried to de-throne King Joffrey. He was also present when Ser Barristan Selmy was dismissed of the brotherhood

In the books
In the Song of Ice and Fire novels, Arys Oakheart is a member of Robert Baratheon's Kingsguard. He's a member of House Oakheart, a noble house from the Reach