What are the worst/best ID tools and why?

Hey everyone! I am hobbyist designer (read: guy with a 3d printer) but professionally I'm a software guy. I am thinking about working on a side project that will use Augmented Reality to help designers.

I have been working with a few small firms to try to get a better understanding of the challenges of ID and I would love to hear what you guys are thinking.

What do you think are the best/worst ID tools and why? Is there anything that you wish you could do that you can't right now?