I use all my gadgets at one time or another but some of my favorites are
1. Big Look
2. Gypsy Cutter (for chain piecing)
3. Clapper
4. Steady Betty
5. Hot Hemmer ruler
6. Add a quarter ruler
7. Zirkel magnetic pincushion
8. rotating mat
9. Bias tape machine
10. Sidewinder
I have the Go and over a hundred dies but I consider that as essential as my sewing machine.