Nethack
Pet games, or virtual pets, are what compujunkies that can't take good care of an actual living organism play with. There's virtual cats, dogs, plants, and, of course, Tamagothi and all that. However, the best of the bunch is clearly the Creatures line. In Creatures, you lead a bunch of cute little furry things out of danger, and to greatness. This game is neat, as there's strategy (How to keep your cute fuzzy things alive and happy), there's a goal (Getting rid of the bad critters), and there's nuturing/pet stuff.
But that's not why this game gets anything. It's the underlying program that really gets our attention. It's biologically realistic enough to satisfy even your high school biology teacher. The Creatures have actual genetics! There's heredity, there's mutation, a whole bunch of fun stuff. You can even mess around with the genetics editor. Make some mutant cute furry things.
And did we mention that they're cute?
