Gimbal is the multiplayer shooter with buildable vehicles. Customize your weaponry, engines, and accessories, and then take to the skies against other pilots in real time. - Top-Down 2D Gameplay - Real Time Multiplayer - Rigid Body Physics Engine - Completely Customizable Vehicles
I purchased that game on Indiegamestand and...i cannot say i really happy with it.
I seen such games before, even free. Gamepad support is very buggy. Only online. No upgrades without real kills.