07 - Favourite Antagonist
Another easy choice:
I love the struggle between Sméagol and Gollum, I can relate to the fact that the Gollum-personality is a corrupted form of the lovable and rather sweet Sméagol, I understand where Gollum's hate and scheming are coming from. He is -together with the Nazgûl- the ring's corruptive power come to life.
And yet, despite the long time the ring poisoned his mind - there's still good in him, there's still the side of him that one could like, and maybe even love.
Gollum is the driving force of the Sam-Frodo story-arc. While Sam certainly is Frodo's strength, his support and his most loyal companion, it's Gollum who calls the shots and ultimately leads them into Mordor and quite literally to victory. Without Gollum's addiction to the ring, without his need to re-possess it, Frodo would have walked away from the fires of Mt. Doom the same way Isildur did. He would have failed his quest, and not even Sam could have stopped him there and then.
Gollum in a way is the real hero of the story - because in the end, Middle Earth would have fallen without him, even if his part of the solution was quite accidental.