It’s basically a giant cheese slicer with a super thin wire. It’s on the expensive side (retails for about $30). When so many of our clay hand tools cost $2 – $5, this is a bit of a jump up. But it really a tool that I use every day, throughout the day in my studio, so for me, it’s definitely been worth it.
I use this for the Mudtool Mudcutter for 5 basic studio tasks.
Here they are (in order frequency):

• I use it for cutting clay when I’m weighing out uniform pieces. I can cut the clay using the Mudcutter with one hand (my right) and then I can pick up the chunk of clay with my left hand, put it on the scale to weigh it. I know it doesn’t sound like a big deal, but it shaves a couple seconds off each time I weigh a piece of clay. It adds up! 
• Cutting feet on plates and platters:
• Cutting off the exess clay from the bottom of a handle on a mug.
• Faceting!
• Cutting a teapot spout at an angle to fit the body of the pot. The super thin wire doesn’t have much drag, so you don’t distort the spout.

There are more uses for this tool, but those are my top 5. The 2 parts that make this so tool unique: The very thin wire that cuts through clay without drag, and the depth of the area between the wire and the frame.

One time, a couple of years ago, the wire snapped. I ordered replacements… and it turns out that they were out of stock. I had to wait about 6 weeks for the replacement wire. It was hard being without it. I now have a couple stashed in my studio so I’ll never be caught without a replacement again.

I don’t know if this is a tool that would be helpful to you, but it’s one of my “must haves.” I had no idea when I bought it that it was going to become a tool of daily use for me.

What are some of your favorite tools?