Toposolitario has uploaded a terrific free paper model of a steam mecha. It comes in several colors and varieties and would fit in with a steampunk, Weird WWI or Weird WWII theme.
mech
Classic Battletech Rules
Classic Battletech is a free 24 page set of rules for playing the original game of giant robots on hex maps.
Fast Play Mech Rules
Outland Games presents “Fast Play Mech Rules.” As with a roleplaying game, you begin by rolling up a mech. The entire set of rules occupies just one page.
Mechbrawl Card Game
Mechbrawl is a free expandable card game. In it, you face off against your opponent in a giant, customizable war robot.