Warframe. It's free, has engaging combat, can tame animals, has a metric crap load of weapons, skins for pretty much anything that can be attached to your warfame,lots of theory crafting, other things and updated ridiculously often. We just got a new warframe (Sevagoth)in the current update & we'll be getting another new one (Yareli)in the next major update.
Here are the official updates directly from the developer's website if you're curious:PC Update Notes - Warframe Forums
Edit: You can see almost all of what the game has to offer on its Fandom wiki:WARFRAME Wiki | Fandom
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