Unity is one of the only 3D engines that could be recommended to beginners. It's a powerful engine capable of just about everything you'd want from a 3D game. It's capable of importing models from most 3D packages and it has a comprehensive editing suite that allows you to put much of the content of your game together before you add any code. Games made with Unity can be exported to Windows, Mac OSX, Linux, iOS, Android and Flash.
While Unity is a very easy engine to work with, it does require basic coding abilities and so may not be the best choice for people just starting out. The free version of the engine is very capable and allows you to release commercial games, however some advanced features require you to buy the pro version of the engine. An additional paid licenses are also required to export games to iOS or Android.
- Download Unity
There is now a real glu of Unity learning resources including many books and websites. Here are just a handful of free tutorial sites to get you started.