For my personal list, I'm going to stick with the "Traditional" Drop tower design. Mystery Castle is a completely different experience. Don't get me wrong, I love that ride, but it just doesn't feel like a drop tower to me.Mystery Castle is a tower that drops you down = drop tower
That is also happens to be a "Shot tower", makes it even better
Take Croc Drop at Chessington World of Adventures for example. I've ridden it, yet I do not rank it. Most would describe it as a drop tower, but because it's not a complete freefall from the top to the breaks, it's not included.