Bill the Pony
Once upon a time, Bill the Pony was property of one Bill Ferny, an evil, crooked Man from Bree who, along with a squint-eyed companion was widely beleived to be responsible for letting loose the horses and ponies from the stables at the Prancing Pony. Actually, it was an irony that he alone had the only pony left for sale within Bree on the day Strider, Frodo and company were planning to leave.
Yet, it seemed Bill was more than eager to depart from his cruel master and work tirelessly in the service of Sam Gamgee, who immediately adopted Bill with great affection. As it happened, Bill proved an invaluable member of this early fellowship, making his way to Rivendell, improving in health and strength very quickly. Actually, Bill became rather a talent at picking out paths where none were apparent, proving more useful than a simple pack-pony.
Bill The Pony was the last member of the Fellowship of the Ring that departed from Rivendell, loyal as he was carrying much of his companions burdens. However, it was at the Gates of Moria where Bill was to destined to depart and made to break from the fellowship. With wolves howling and the Watcher in the Water revealing itself, Bill bolted away as he was supposed to, hopefully surviving long enough in the wild to make it to safe pastures and eventually Rivendell. Yet, it was not in fact Rivendell where Bill joined Sam once again, but in Bree, looked after by Nob the Hobbit, who cared for him when he turned up looking somewhat the worse for wear. So it was that Bill returned with Sam and lived out his remaining days in the Shire, well travelled and in better care than the day he was found by Sam, his best friend and companion.