Honestly, you can probably make due with just about whatever you currently have at your home. I don't recommend going out and buying one of those special pumpkin carving kits. Those are probably a good idea for small children who should not be handling sharp knives, but for an adult, almost any regular knife would work better.
Here is the exact knife that I use for 99% of my carving. It is nice because it is light, and has a thin and flexible blade. This is great for shaving the skin off the pumpkin and cleaning out the teeth.
For cutting off the top, I would use a standard kitchen knife that is strong but not too wide. And for gutting the pumpkin, I use a standard serving spoon with a somewhat sharp edge. I tried to find my exact one online but it does not even have a brand name on it so it was hard to track down. If you don't already have this kind of a spoon then you should be able to get one for under 10 dollars.