I think the current king-of-the-hill in terms of power requirements is the Intel quadcore:
ftp://download.intel.com/design/processor/designex/31559401.pdf
page 18: 1.1V, 125A, 130W design power.
I think some of the older Pentium D's were pretty close to this as well.
They stopped drawing power from the 5V lines about when the pentium 4's showed up. The last motherboard I had that had that configuration was a AMD dual socket one - the main failure mode of that board was for the 5V pin on the power connector to melt (2x 50W@5V through 2-3 pins just isn't healthy).