Warframe

Warframe is an online free-to-play cooperative third-person looter shooter. In the far future the Orokin had absolute control over the solar system but have since disappeared, now the militaristic Grineer, the money-worshipping Corpus, and the Infested fight for what they left behind. You are a Tenno - a master of gun and blade and user of the Warframes, it is up to you to bring back balance to the system from within, while also fighting a new threat from without: the Sentients.
Over 40 unique Warframes to build, hundreds of guns and melee weapons to utilize, and various pet companions to help you along the way - all of which can be crafted for free and enhanced by an in-depth modding system.
With constant updates by Digital Extremes, the game now has over six years of updates including new open-world landscapes (Plains of Eidolon-2017, Orb Vallis-2018) and cinematic story expansions (The Second Dream-2015, The War Within-2016, The The Sacrifice-2018) with more content being added every year.