All this data is potentially out of date, and should be taken with a truckload of salt
MTACs (Mechanized Torso-Actuated Chassis) are metal exoskeletons used for heavy duty mining work. They are armed with mining lasers and can be remote controlled or worn by miners.
MTACs make for effective emergency weapons in combat, as they are heavy, virtually immune to anti-personnel laser weapons, and have large, dangerous claws. Some have surface cling abilities that allow them to maneuver in zero gravity.