A cutter to cut PVC, Cor-X, paper, vinyl, acrylic, banners, gatorboard, laminate, cardboard, shocard and probably other things. The Keen or Fletcher would be my recommendation. They start around 24" or 30" up to about 12' long. Our one is 126" and the other is 65" with a laser eye for accuracy.
What size do you do the most of ?? That will at least get you in on the ground floor. Think ahead, cause you don't wanna buy cheap and in 2 or 3 months have to get another one a little bigger. Plan ahead.
We do a lot of printing on 5' x 10' PVC, so 124" made sense to us. It works fantastic and can cut hours off of jobs depending on what you're workload is like. We can do in a day what used to take us maybe 2 or 3 days.... with far greater accuracy. I mean, the cuts are dead balls on.