Sablés Nantais Tools
R & M International
These are great for biscuits too. Frankly, I use them all the time for various projects.
Rolling Pin Guides
Using these is a great way to ensure that your cookies are even. You get 3 different widths, and they are great for pie crusts & croissants as well.
QUDUME
These are flat sifters that are great for your kitchen arsenal, I prefer them to the round, strainer type sifters. They come in a set of 3 sizes.
NORDIC WARE
This may seem like a no-brainer, but not all cookie sheets are created equally.
I love these because they are rimless, which means the heat can circulate around each cookie. Also they are aluminum, (not the dark non-stick metal that was all the rage-which tend to make your bakes dark in places as well)
Personally I have 4 of these, that way I can be baking 2 batches in each of my ovens at the same time.
FUN FACT: The edges are so thin I can actually use these as a PIZZA PEEL!