Rust is a base building PvP survival game available on Steam.
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Pros
Pro Non-PvP servers are available
If worrying that another player might kill you and loot your corpse is not your thing, or if you don't want to deal with someone constantly harassing your base, there are servers available that take away the risk of other player's malicious behavior.
Pro Building system is simple, efficient and intuitive
Hold a key while holding a hammer, and with your cursor, select the piece you want to build.
Upgrading a piece of building is done in the same fashion.
Pro Game's multiplayer nature creates psychological tension
While there's obviously potential for working together with other players towards achieving certain goals, the more likely scenario is someone trying to kill you to get your stuff. Or even worse, deceiving you in working together to achieve a particularly difficult goal only to stab you in the back when you're not needed anymore. It's easier to take stuff from someone else than gather it yourself. And since your base is a the perfect bullseye to other players, there is constant threat of griefing.
Pro Lots of variety in ways to die
Fauna, including bears and wolves, is trying to kill you, radiation, that's ever-present, is trying to kill you, zombies, in a multitude of colors, are trying to kill you, other players on the server, equipped with guns, are most definitely trying to kill you, and you, yourself, if you don't find food, will die.
Pro Base building allows for less punishing gameplay
Because you can build your base that you respawn back to when killed, losing only what you had on you at the time of death, it allows getting back to where you left off quickly.
Cons
Con Hard to play solo
Rust is all about clans fighting for territory and loots. Solo players (or ones with a couple friends) can easily be killed by bigger clans.
Con Not yet finished (buggy)
Since it's a Steam Early Access game it still has lots of glitches, placeholder text and unreliable infrastructure. But for all its unfinished nature, it's surprisingly playable.