Bilbo BagginsBilbo - The hobbit who started it all.  By finding the Ring of Power, he set events in motion that would result in the War of the Ring.

 

"The party was assailed by Orcs in a high pass of the Misty Mountains as they went towards Wilderland; and so it happened that Bilbo was lost for a while in the black orc-mines deep under the mountains, and there, as he groped in vain in the dark, he put his hand on a ring, lying on the floor of a tunnel.  He put it in his pocket.  It seemed then like mere luck." ~The Fellowship of the Ring (Prologue)