Try and recreate the magic of the sleeper hit RPG that took us all by storm. The simple aesthetic of Undertale makes it an ideal game to model some kickass pumpkin carvings after.
This carving of Papyrus nails his toothy grin and anatomically impossible (yet expressive) eyebrows. Perhaps you could finish the job by dressing up in one of the various costumes that he dons throughout the course of the game.
If you want to try something a little more complex, though, you can use this stencil to recreate Flowey -- the kill-or-be-killed antagonist of the game. Keep in mind, though, that this will require some shading as you carve. The center of Flowey's petals cannot be cut out entirely, or you'll lose the facial features. Instead, you'll need to carefully shave this part down so that light shines through, but his expression is still intact.