[Oberon]

A denser than Earth substance would allow one to get closer to the gravitational center so that less mass would be required to obtain 1 g. As it happens if one could stand on the core of the Earth one would experience 1 g. (The massive core still being to much to launch.)

Read the fine print, dude...I didn't write "as much as the Earth weighs," I wrote "as much as a planet weighs." Even accounting for a high-density object permitting closer proximity, you'd still have at least a Mercury's worth of mass to lift off the ground.

[Poincare]

What is your problem? Dude?

The bottom line is that the denser the mass, the less that is needed. BookaT mentioned the idea of a super dense mass. Such things are in our universe, just not on Earth in any quantity. If there were a way to assemble a mass of, say, concentrated neutrons as found in a neutron star, it would merit consideration. If there were a way.