Another would be the game Faster Than Light.
The game revolves you, your crew and your ship. The Galactic Federation has been all but destroyed by Rebels but you have critical data that can defeat them. Somehow, you have to jump across enough sectors using your faster than light warp drive to deliver this data in one piece.
And this is all while the Rebel fleet is right behind you, trying to catch up and stop you. Each sector contains an exit that will allow you to jump to the next sector, and every sector is broken up by various waypoints which your ship can jump between.
Everytime you play the sectors are randomly generated so it's a new and unique experience each time.
Sound simple so far? Here's where it gets tricky.
Here we go...
I know I have several Sci-Fi fans, people who loved shows like Firefly, Star Trek, and Battlestar Galactica. Who's ever wanted to command their own crew? Yell at someone to fix the engines because a volley of enemy missiles have damaged them. Meanwhile you divert power to the shields to protect the ship but intruders have boarded so you need to to stop them too. You target your own lasers to destroy the enemy weapon's array but by now the boarding party has already destroyed the oxygen generators (causing your crew to slowly asphyxiate).
At least someone is extinguishing the fire in the medbay.
FTL lets you do all that and more. Every possible function and upgrade in a starship is available to you. Every system of your ship requires power to work, upgrading a system means it needs more power and with limited power you have to balance and make sacrifices to survive. I play extremely defensively, maxing out my shields, grabbing cloaking abilities, and using weaponry that disable enemy systems. My friend prefers to max out on offensive weapons, destroy your enemy before he touches you. I've see other people use automated drones or send their own crew to infiltrate other ships.
Every waypoint you travel to has a chance of an event happening. It can range from a simple automated Rebel scout attacking you, to answering a distress signal, or entering an asteroid field with Pirates waiting. And you could just decide to run away from a fight, sometimes distress signals are traps, and maybe the Pirates upon realizing it was a bad idea to attack you, beg for their lives. But it's up to you to spare them or not.
Every jump is random!
I'd recommend FTL to anyone with any interest in the Sci-fi genre. It is not an easy game and it's not a forgiving game either. If any of your crew members die, it's permanent, shops and repairs are uncommon and who says you can afford their wares anyways? All it takes is one bad encounter to cripple your ship for the rest of the mission and if you die, you have to start over.
And you'll want to start over. Just one more time, maybe you'll be luckier, maybe you have a better idea of how to do things, or you could be just masochistic. Whatever your reason, FTL has additional unlockable ships, achievements, high score recordings and potential for modding. Available on PC, Mac and Linux for only $10 on Steam I thought it was well worth my money. I even ended up buying the soundtrack but that's because I liked the electronic music in it.