Car mechanic David Harr, from Seattle, realised he needed to devote 40 hours of playing just to earn the final reward points for Perfect Dark Zero.
He built a machine that would start and re-start the game to register for the final achievements he needed.
"I reverse engineered the problem and came up with the xBot," he said.
Xbox 360 games come with up to 50 different achievements for gamers to unlock.
Each achievement carries a different points reward, which is reflected in the player`s overall gamer score.
Some of the achievements are unlocked by completing levels, but others are more challenging - pulling off a series of spectacular headshots, or doing a 360-degree turn in a racing game, for example. To win those final 60 points in Perfect Dark Zero Mr Harr realised he simply needed to play 2,000 offline matches in the game.
"I calculated that it would take about 40 hours of gameplay just pushing two buttons to start and re-start a game," he said.
"With my electronics experience I wondered if there was something that could push those two buttons for me so I could go about my daily life."
Using $60 (£32) of electronics parts bought from a local shop and some parts he had "just lying around", Mr Harr built his xBot machine in about 10 hours.
Two solenoids in the machine press the buttons when required so that the game starts at the right time.
Some gamers, writing in online forums, have accused Mr Harr of cheating.
"This is not playing online on Xbox Live - it is not playing against other people. That would be unethical.
"I asked myself: `What type of rewards would be coming out of the effort of doing this?`.
"If I was recording button presses and joystick movements and duplicated that to help people bump up their scores, then there is money involved - that would not be ethical.
"This is a one trick pony, getting you just 60 points. It`s not stepping on anyone`s toes."