Having been a HP fan for nine years (and counting), I've had many.

The most interesting one was right after GoF had been released to theaters. In fact, I think this dream might have happened the night of the day I saw it. In any case, I dreamt that I was in the graveyard watching Voldemort be reborn. It was just like the film - except that after Harry transports back to Hogwarts via the Portkey, Voldemort decided he was going to profess his undying love for me! Which, at the time was good, but looking back...wow. That was a rather creepy dream.