I have to admit, I've had a silly amount of fun in Voxel Turf. A game that combines the block-building that made Minecraft popular with vehicles, buildings, gang wars and all sorts.
The latest update is a pretty big one adding in a Light Plane, a Commercial Airfield along with a version for bandits, Steam Workshop support for maps, a massive map that covers the world which you can grab from the Steam Workshop to play, the ability to generate in-game maps from bitmaps and more.
Flying around in a plane is a pretty sweet way to travel the city:
Have a look at the latest update video to see more in action:
It's a rather strange game overall, one that blends together multiple genres into one. Surprisingly fun though, especially taking down a bandit base when you're having a break from building up your own commercial empire.
Find it on Steam.