My favorites are from Swiftwick in the the Pursuit line (which are a merino wool blend). They're lighter weight on the top of the foot, but the bottom/toe/heel area has thicker, but very soft napping. The come in varying cuff heights, as denoted by the number (Pursuit 4 has a 4" cuff, etc). Expensive, but awesome.

Runner up would be from Smartwool, in the "Light Elite" weight, which can be tough to find. Similar to the Swiftwick with targeted padding in the bottom/toe/heel areas.