MAC is on the top of the list for everything but foundation and concealer. I been dabbling in NARS lately which I LOVE. And of course, mineral makeup I like Everyday Minerals
My favorite brand is Stila, but if you were to look through my stash, there would be such a huge mix of lines! Lately I've been on a Bobbi Brown & MMU kick (mostly LaurEss foundation & Signature Minerals blush).
I'm definitely a MAC fan... but if I were to buy some other stuff I would feel comfortable in buying Bobbi Brown and Smashbox. I haven't tried Shiseido, but I've heard nothing but good things about them. I'm pretty eager to try them. I like a lot of their color eye shadows... very bright and bold!