An enterprising indie developer pointed me toward his 3D pumpkin carving game on Xbox Live Indie Games called Pumpkin Chop.
As virtual arts and crafts go, it's a pretty satisfying experience. There's spooky music, a lot of freedom with the carving function and a Show Off! mode that features eerie settings in which to view your finished jack-o-lantern.
Having played the demo versions of other pumpkin carving sims, I've got to give Pumpkin Chop the top nod for allowing users the most freedom. Other carving sims either make you use pre-made cutouts to makes your pumpkin's face or just don't let you savor your lit up pumpkin the way that Pumpkin Chop does.
My only gripe about the application is that there's no scraping-out-the-insides portion. You could totally turn that into a fun/gross mini-game.
Check it out, if you've got 80 Microsoft Points to spare. If nothing else, it's a lot less messy than the real thing.
Note: A code for this app was provided by the developer for reviewing purposes.