This is the mother of all concealers!
MAC sells this as a foundation, but it's the same formula as their Studio Fix Concealer in the little black pot. This comes in a full-sized compact, and there's a ton of it in there! I doubt I'll ever get to the bottom of it, and I'm a concealer freak. I bought this off eBay, so I'm sure it's a couple of bucks more from a store, but it'll be worth it because it'll last forever. If you like a thick, dry consistency that blends well but stays opague, this is for you. I like to apply it with my foundation-soaked sponge - it really melts in but covers like crazy. Great value!