Studio fix fluid.. I've got 3 bottles, nc20, nc 30 and nc40 depending on what time of the year! It's my HG foundation that I can thin out with moisturiser or use straight for a perfect finish.
I know it's not the kindest to every skin, but I feel weird if I don't have a compact of Studiofix with me. The color range is better than any of Mac's other foundations, and if I have to redo my makeup quickly I can in one swipe.