Samwise Gamgee
Gollum began following the Fellowship of the Ring in Moria, but was noticed by Frodo Baggins, Gandalf, and Aragorn. He trailed the Fellowship to the edge of Lothlórien. He picked up their trail again as they left, following them all the way to Rauros, then pursued Frodo and Samwise Gamgee across the Emyn Muil when they struck out on their own towards Mordor.