Gather your supplies:
Xacto Knife Handle
Xacto Keyhole Saw Blades
Xacto Router Assortment (scraping/digging)
Large Nail (yes really)
I think it's about $5 for the Pumpkin and about $40 for the knife set. I bought the knives about 3 years ago and I'm still on the same blades.
If you are reading this, but are just going to end up carving a 2 dimension pumpkin (light and dark), the Keyhole Saw Blades are awesome and beat the grocery store kit saws hands down.