Samoflange densest known material in the Vendetta Online™ universe. It is a trade good, and masses 8000 kg/cu. Leviathans and capital ships will sometimes drop this substance. There is at least one mission that gives Samoflange after successful completition.
To relate this density to real world materials: in the game, 1 cu of water is 100 kg, given that water is 1000 kg/m³ that means a "cu" is 0.1 m³ (excluding the mass of the container, of course). Given that, the density of samoflange is 80,000 kg/m³.
For comparison, the densest known element is Osmium at 22,610 kg/m³ and the core of the sun is about 150,000 kg/m³. Some have speculated that samoflange is neutronium, but that is far more dense, by 11 orders of magnitude (assuming they mean matter from a neutron star).