Book Nook in a fireplace that is no longer usable. Very creative use of space. Just make sure to clean that fireplace well before putting any books in there and to seal things to prevent water damage or pests from coming down the chimney.
Fall / Halloween / Autumn - loving the pumpkins all in the fire place, very creative way to make it look appealing, love! But not the main fireplace! I don't love anything more than a fire going in the fall :)