Manolo Blahnik, hands down. They may look uncomfortable, but trust me, you could walk for hours in his masterpieces. I once wore his Carolyn slingback for over 12 hours...no problem.
It definitely has to do with the flawless construction and materials. The sole is flexible and grips the ground. There is elastic in the slingback over the ankle, and that provides more flexibility.
If you're looking for an everyday shoe, go for a wedge. I highly recommend Michael Kors "Peru" suede wedge. I have two colors (orange and t.moro brown), and they have lasted and lasted. The back heel has worn out, so I re-heeled it, but the sole is awesome because it's all leather. The more wear, the more character it gets. It is nearly 4" and super comfy because it's a wedge. The stacked heel is so much more elegant than a crepe (plastic) heel you see on cheaper shoes.
KORS Peru can be found on zappos.com