Mouse Trap is an interesting game for the Atari 2600 because it uses the fire button to perform two different actions!  It was first released by Coleco, then several years later by Atari.

Mouse Trap is similar in play to the Pac-Man.  You are a mouse inside of a Pac-Man like maze.  Instead of being chased by 4 ghosts, you are chased by 3 cats.  You run around the maze trying to pick up all of the pieces of cheese (like the dots in Pac-Man).  In each of the four corners, there is a bone which you can use to turn yourself into a dog and chase the cats.  Here is where the game differs from Pac-Man...you pick up the bones and save them until you want to use them.  QUICKLY press the fire button to turn into a Dog.  If you press and HOLD the fire button, some of the walls of the maze can be moved to block the cats.  This multiple action for the fire button is very uncommon for the Atari games and makes Mouse Trap a bit more interesting.  Also of interest, you can move the walls to block yourself in the center of the maze, away from the cats, to basically pause the game.  This is a particularly important feature for mousetrap because the game is so easy to play that one game could last for days!  This is a relatively easy game to find for cheap and it's pretty fun to play too.