Colossus

The Colossus is a Protoss ground unit.

Armed with twin beams, the Colossus is especially effective against large numbers of weak ground units. The long legs allow the Colossus to cross between terrain of different elevations that other ground units can't pass through. While powerful against ground units, its weapons can not target air units.

The Colossus appears to be inspired by the tripod walkers from the novel, War of the Worlds.