Warframe

Warframe is the best free-to-play games that I've encountered. It is NOT pay-to-win, like many other games and apps are, and there are no story expansions to pay for. Every Warframe, weapon, and all the equipment can be obtained and built for free--it just takes time. You can get a lot of the cosmetics for free, too, you just have to be patient!

The game has beautiful graphics, even on low settings, and the environment and character designs are wonderfully unique. No two Warframes look the same, even if you're wearing the same frame as someone else--the customization options are impressive, even if you don't sink any platinum (the game's purchasable currency option, as opposed to the credits you earn on missions) into cosmetics. The music and sound engineering is also great, adding so much to the atmosphere of missions and quests.

Warframe's writing is fantastic. The main quests (referred to as cinematic quests because they include dramatic cutscenes instead of the characters just speaking over comms) are rich with lore, and there hasn't been a single one that hasn't made me feel a lot of emotions--several have them have even brought me to tears.

I highly recommend the game to everyone. If you like third-person shooter games, action games, sci-fi games, RPGs, aliens, robots... It's not an inherently competitive game (they do have PVP modes, but they're not mandatory), so it's still fun for people who don't like fighting other people. It has something for just about everyone, and it's a great game to play with friends.