Actors Daniel Radcliffe and Emma Watson paid tribute to their 'Harry Potter' co-star, late actor Robbie Coltrane.Best known for playing the gentle half-giant Rubeus Hagrid in Harry Potter, Robbie died at the age of 72 on Friday night. His agent Belinda Wright said he died at a hospital in his native Scotland. She called him "forensically intelligent" and "brilliantly witty" in just one of many tributes made to him.