My favourite mecha unit in Code Geass is definitely the protagonist Knightmare Frame 'Lancelot' piloted by Suzaku Kururugi. The basic unit has a clean design befitting a knight. The design is pretty awkward with the pilot cockpit protruding at the rear. The unit has wheels on the foot for additional speed like rollerblading.
Lancelot uses VARIS rifle at long range and 2 Maser Vibration Swords for melee. An extra and unique armament are the Slash Harkens on hip to swing and hook. For defence, it forearms are mounted with energy shields. I bought both Code Geass Robot Spirit Lancelot and SD Lancelot to pose them the same.