Some tools just don't work very well.
Big Knife - Only a hack would use a giant knife to remove the top of a pumpkin. If you don't have a sawzall handy and must use a knife to get through the thick area at the top of the pumpkin, use a boning knife. The blade is thin enough to carve a somewhat round cap. Otherwise your cap will look like a retarded stop sign.
Dremel tool / Roto-zip - Man, I thought these two would be great at carving. I even bought a "carving" tool for my dremel. I had high hopes. Unfortunately, I never considered the fibrous nature of the pumpkin. As you try to carve a straight line using a spining carving tool, it will slide through some spots and then snag a fibrous spot and jerk to one side. These two tools just don't work. Use a jig saw for carving and you'll be much happier. The in and out motion is much easier to use.
Note: In 2007, I started to use a dremel stylus tool to do some fine carving work (like detailed teeth and such). It works fairly well, but I wouldn't suggest it. The dremel stylus is held in your hand, like a pencil, so it easy to keep steady. For this reason, I have started to like it.
It is mostly useful for super-fine detail work and not good for actually carving a pumpkin. I still suggest a jigsaw for most work. Besides, the dremel stylus costs something like $75.00, so unless you have to do a special pumpkin for a talk show or something, I suggest you invest your money in the beverage market.
A Torch - Trying to burn a pumpkin is like trying to light a block of ice on fire. They are mostly water. A torch doesn't do much.
Circular / Miter / Radial Arm Saw - If you want to slice a pumpkin like a loaf of bologna these might work, but for anything else, forget em. If you want to take a slab off of a pumpkin to make it sit or lie flat, a cross cut hand saw will do the job in no time. Pumpkins are soft and easy to cut.
Here are some links to pumpkin carving tools that I like to use. I tried to spend some time to find you guys great deals. I think I did a good job of it.