ApeTown is a Minecraft server built around a never reset world, with a free for all PvP setup and only 2 rules to keep things simple. It stays pretty close to vanilla survival, so you get the usual survival grind and freedom without a bunch of extra clutter.
You can do pretty much anything you want here, which means base building, exploring, fighting, and causing a bit of chaos if that's your thing. Just don't hack or lag the server, and you're good.