The Atari 8-Bit version of the classic Mercenary is the original, published by Novagen in 1985.
From the opening sequence onwards you know that you are in for a special ride with Mercenary, and exploring the wireframe world of Targ (the name of the planet you’re trapped on) is a video-gaming joy – especially with the easy-to-use controls.
There are items to collect, different vehicles to drive/fly, landscape features, two warring factions to exploit, underground complexes, and various secrets to uncover. Mercenary is packed full of detail although it may not be apparent from the outset.
The Commodore 64 version may be more famous, but this Atari original is fast, smooth and colourful – arguably better. And perfectly playable/enjoyable in this day and age.
More: Mercenary on Wikipedia