A classic space sandbox with many ways to play. Smuggler, explorer, bounty hunter, and more are all viable career choices. Every ship is highly customizable, and the trade gameplay is backed up by a fully simulated economy reminiscent of Eve Online's, all in a single player game. Every raided trade convoy, every ton of smuggled goods affects the economy.
The combat in this game is the standard against which all other games of this genre should be compared. Endless Sky, SPAZ, and the rest are all fine, but none can come close to the sheer satisfaction that this game's combat brings. Top down space combat and fleet command combined with excellent design and hyper-competent AI make for an incredible experience. You pilot your flagship, and can issue commands to the rest of your fleet, who will then follow said commands to the best of their ability.
The combat in this game is slick, stylish and satisfying. Every ripple on the energy shields caused by salvos of autocannon slugs, every missile salvo, torpedo strike, all has a euphoric satisfaction to it. The AI (both on your side and the enemy's) will micromanage their shields, dodge incoming fire, ruthlessly exploit any momentary vunerablity in an enemy ship, know exactly when to withdraw to friendly forces when out-numbered, gang up on and flank larger enemy ships, use enemies and allies alike as cover from enemy weapons fire, and more. Even the missiles are smart enough to seek a new target when their current one is destroyed.
If that's not enough to recommend it, this game has mod support, and a highly active community developing said mods. New factions, hundreds of new ships and weapons, total conversion mods, and more. There are mods out there with transforming space mecha ships. What more do you need?
This game is technically still in development and updates are slow, with major updates coming out about every 6-12 months, but considering the amount of content already in the game, and how few and far between bugs are, it is perfectly reasonable to treat it as a finished product, and think of each new major update as a free DLC, adding new systems and content on top of what could already easily be a finished product by itself. The devs are very communicative about their goals with the game, actively seek to squash any bugs, rework existing systems to make them more enjoyable, and are very open to community feedback.
If you don't mind a bit of a learning curve, and love awesome space battles or want a fun, open ended space sandbox, get this game. This is the definitive game of this genre, and there are many hundreds of hours of fun to be had trading, smuggling, exploring and fighting your way across the sector. At the time of writing, it's 15 USD for a CD key, I'd highly recommend giving it a go.