I like ManiacQuilter's idea. Or a ShapeCut. I cannot cut the right size to save my life & the ShapeCut ruler has really helped to get even cuts that are on-grain every time. The other thing I have that everyone always asks about when I go to classes/workshops is my IdeaWorks travel light. It is battery powered & comes with a charging cord to connect to a computer, but I just grab the wall plug for my iPhone & it connects to the wall and gets even brighter. Here's a link:
http://www.amazon.com/Super-Bright-P...deaworks+light
As far as anything else, it really depends what kind of quilts you like to make. I could suggest some other gadgets, but they mostly focus around my love of applique.