[Quiet Man Cometh]

That's a bit of a toughy for me because I'm not all that fond of Tolkein's writing. Off the top of my head though, the battle of Pelanor fields stands out to me (that's the one in front of Minas Tirith, right?). Hoever, it might also be that one because it's the most recent one I've read. It's been a while since I've read the other books. I remember liking the sequence after the battle of Helm's Deep when Fangorn forest is parked outside the door and waiting to beat up on the orcs. It makes me think if there's any other author out there that could pull off a mobile attacking forest.