I have used a dremel 4000 one year. you can use any of them just perfer a slower speed. The one Mr_Synical was referring to, is a low speed battery powered one. As a haunter I personally wouldnt waste my money on it but not everyone is a DIY.
Since Funkins are soft you can use almost anything.
If you're just cutting then use cutters like:
The Pumpkin dremel uses a High speed cutting bit "100 High Speed Cutter "
I found the "561 MultiPurpose Cutting Bit" to be pretty good at cutting foan holes.
if you are adding some thin lines use an engraver bit.
I do recommend getting a spare one to practice and test bits to get the desired speed and control.
Yes, I have. You need this : dremel flex shaft- much easier to control the small intricate carvings. Battery operated? not as powerful as plug in. Don't waste your money. You need the bit that looks closest to a small drill bit. you can look on my pinterest board link below under the dremel made me do it board.
As noted the flex shaft works great as holding the main tool with slippery pumpkin hands is tricky.
My preferred tool last couple of years however is a jig saw. This is the cat's you know what for cutting off the top and any bigger/course work. For fine detail I made a tool out of fatter grip xacto style handle and a 6" piece of old scroll saw blade. Cuts very fast/easy with absolute precision.
I use my dremel for the funkins and the foamies from Michaels. I was using the bit that stonykins suggested (1/32") and I broke two of them (one is less than 5 minutes). I will be looking for a better bit, perhaps the Rotozip-type bits. I grabbed 4 funkins from Joanns, including the giant ones