Alterac Valley sets my towers aflame. I fell in love with AV during classic WoW, in those sprawling, drawn-out matches that spun out over a day or longer. With a big map and plenty of time, you can savor the micro-encounters that make up a true battle -- that exquisitely frozen moment when you come face to face with an opponent behind a bunker, the off-objective chase that neither of you will give up, the "happy" grudges that leave you seeking out the same opponent the moment you respawn. I gulp down that stuff like water. Objective-driven play has its appeal, but it's the serendipitous moment of connection with the enemy that really turns my flag.
I have a friend who adores siege weaponry. For him, PvP queuing means a beeline for Wintergrasp, Strand of the Ancients, or Isle of Conquest. That's fine. While he's staying busy with catapults and cannon, I'll be slowly throttling some newly met nemesis in the somber shadows behind the keep.
What do you enjoy most about your favorite battleground? Is it something that's there by design, or is it some player dynamic or bit of byplay that fires you up?