Unity - The multiplatform game creation tools for everyone.
Hill Climb Racing 2 - Sequel to the most addictive and entertaining physics based driving game ever! And it's free!
Godot Engine - Feature-packed 2D and 3D open source game engine.
Alto's Adventure - An endless snowboarding odyssey
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Happy Wheels - The fun Happy Wheels game features several levels that you have to get through using a variety of wheeled vehicles. There are obstacles that are quite challenging. Read more about Happy Wheels.