Unity is a free to use 3D game engine that offers PC, Mac, and even Web Browser support.
The free licence assumes that you will not be making over $100,000 from titles using the engine in a given year. Although, if you make that much cash I’m sure you won't mind forking out a grand for the license.
The free version also cuts out some features. Can you live without real time shadows, iPhone or Wii support? If you can, Unity is a great tool with a slick user interface and oodles of support. If not you might want to give it a try anyway, if you like it you can always upgrade later.
Importing assets and building your game is easy. However, one of the engines strongest resources is the website. It's chocked full of useful information, tutorials, example projects and much more. Everything you need to know to make your game using Unity is laid out beautifully right here.
Unity even comes with a few book-worthy documents to walk you through every step in making a Platformer, FPS or Driving Game.
• Side on Platformer
• 3D Platformer
• First Person Shooter
• Driving Game
Even if you just pick it up to have a play you’re sure to have a pretty good time with this little gem.