For lack of a better term, I call this gadget a pie server, but you can use it to serve alnost anything that you cut into slices, from cakes to quiche. While it is not intended to be a primary cutting tool, the serrated edge will help with the job.
While there are many versions of pie servers available in a variety of materials, a good stainless steel one like this will last a lifetime.
Expect to pay something in the $5.00 to $7.00 range for a servicealbe pie server. They are widely available and worth the investment.