Ace of Spades
Do you like Minecraft and First Person Shooters?
There’s a game for that. It’s called Ace of Spades.
It’s still a ways until it’s finished, but it’s a heck of a lot of fun. Minecraft with guns is an unfair way to put it, though: You can definitely see where Minecraft inspired Ace of Spades, but the game is paced so differently than Minecraft, and the design varies sufficiently that Ace of Spades stands on its own in a growing Block-based Building Game market.
So, it’s fun, it’s different, and it’s free. You can’t really beat that.
The only real problem is the lack of friendly fire to shoot the teammate that keeps knocking down your structures (Unlike Minecraft, AoS’s blocks fall if there’s nothing below them) and the sickening Voxels that you have to deal with when you first start it up. This is only the second game to give me motion sickness (The first being the original Portal).
It’s something to keep an eye on as it continues to develop.