Fiskars Rotary cutter tool
I use the Fiskars rotary fabric cutter tool everyday in conjunction with a cutting mat and patchwork ruler. This tool is great for cutting easily through several layers of fabric at once or cutting curves easily. A favourite when used with a ruler for perfectly straight lines and angles.
Tool comes in 2 sizes 45+65mm and can be both right or left handed, I personally prefer the 45mm for most fabrics.
Replaceable blade usually included but be careful this is such a sharp tool!