A cutter that you like is a must, but i'm going to throw out there a 12 1/2 x 12 1/2 square ruler as well as the 6 x 24 ones. I'm always trying to square up blocks and I use it a lot more then I thought I would when I got it.
I also say a cutting table that is the correct height for you. I have the one from Joann's and I can't tell you how much better my back and shoulders have been from being at the proper height to cut things out.