Ok, I remember a game, but am not sure what the name was. Let me describe it.
I first saw it on the Commodore 64, and later on the Amiga, but I'm absolutely sure I saw (and played) an Arcade version at one time (I think I'm sure anyways).
In the game, you're a robot on a big ship that's been taken over by other robots. You can "assimilate" them or shoot them. Of course, your robot's guns are weak, and the strategy was to assimilate a robot with big guns to clean the ship out.
Of course, you had to go in stages, as the big-military models would squash you if you just ran up and tried to capture them. Assimilatin required you to complete a mini action/puzzle game. Failure meant loss of a life.
Basically, you moved around the ship from a top-down view, occassionally moving between levels via lifts. If the robot you were assimilating took enough damage, it would get destroyed and you'd have to quickly look for a new host.
Ok, refresh my memory. What game is this, and did it actually come out in an arcade machine form?