Hunter is a 3D action-adventure created by Paul Holmes and published by Activision in 1991 for the Amiga and Atari ST. It is considered the first successful example of a "sandbox" video game based on free-roaming in a 3d environment.
You control a soldier that has to explore several islands, rendered with 3d polygons. You can move walking, swimming or using several vehicles, each one with different characteristics. You can also use several weapons or talk with civilians to gather information. One of the best aspects of the game is the enemies' AI, very sophisticated and capable of complex behaviors.
Hunter received very positive reviews, even if some commentators criticized the somewhat limited world or the lack of several pieces of music. But creating this game, which probably inspired many other games, including the Grand Theft Auto series, was an impressive feat.