Galaga

A great arcade video game. Almost as good as Defender, and better than Qix. It features a challenging stage which is a source of great metaphor.

Space invaders: The black-and-white daddy of all arcade videogames, which effortlessly articulated the frustration and powerlessness of working in a modern corporate organisation;
Galaga: a second generation version of space invaders, with a challenging stage and amusing music;
Defender: A spin on the usual alien invasion motif, where you invade them, trying to rescue little sticky things, and the aliens fight back, and all you have is a thrillingly devastating laser cannon, a small supply of smart bombs and the ability jump randomly into hyperspace
Space invaders calculator: I know it sounds insane, but you could have hours of cosmic fun with an ordinary digital calculator.
Qix: which was really just a bit stupid, but through a design flaw in the game’s basic concept you could play for hours on end if you really wanted to.

All, in any case, useful metaphors for life in a modern multinational investment bank.

See also