I love my FCG too !! That prop just blew me away when I first saw it, probably in Sept. '02. I figured I would make one for Halloween '03, but got so excited about it I got mine built for that same Halloween in 2002. I guess part of the reason the public likes them is because of the graceful way they move and the fact you can't miss seeing it the way the black light illuminates it.
It's hard to say what will be the next FCG. I guess it's personal preference. I like my life-size witch stirring a cauldron and opening tombstone too. Seems like coffin knockers are popular, but I haven't made one.
I'm working on a new animated prop right now that I am excited about and haven't seen built before. I think it's gonna be really cool, but probably not the next FCG.