Arm Servo - The arm servo is an upgrade found in singleplayer only a total of three times. The player is given one for free after the level "The Sniper's Lair", where in a cutscene Glitch re-assembles the droid Spy disguised as a Mil, known as Agent Goff. Goff gives the player an Arm Servo upgrade, the other two can be bought from the Barter Droids.
Switch - As far as the two pole-switches go, they are visibly marked with a green droid hand, or a red Mil insignia. Switches that are marked with the droid hand can be pressed and activated by any bot, signalling they are unlocked. The ones that are red with the Mil insignia say "Mil use only.", because they have been locked out by the Mils. Using one that is locked will typically result in an alarm going off.
Washer - Washers are used as the currency of Metal Arms, they are commonly found by destroying grunts or lying around the map. There is an "oiled" version of the washer that looks red, and is worth 50 washers.
Chip - The standard chip is a pale, sky-blue computer chip, which is commonly used to either activate doors, or Mil control consoles.
Secret Chip - The same model as the normal chip, except almost a golden-yellow. Secret chips are hidden throughout the game, some purchasable from the Barter Droids, and can be collected to unlock multiplayer levels.
Speed Chip - Speed chips are earned by beating a level in under a specific amount of time stated from the level select screen. Not all levels have these, but a good majority of them do. Speed chips also count towards the secret chip count for multiplayer levels.