NeoAxis Engine is one of the most promising and powerful 3D engines of the new generation. It comes with a powerful and easy to use set of tools which contains a resource editor and a map editor. The engine itself supports particle, physics and sound systems, all which are fully replaceable and customizable. The engine's unique architecture integrates those three tools together, making NeoAxis very easy to learn and use for anyone from the inexperienced to the most practiced game developers while retaining the engine's powerful abilities all the way through.
Brilliant engine. All the strengths of a small, fast and powerful rendering engine, wrapped up in the super-easy development environment of C#, without compromising. What's not to love?
You can try it out free, use it for a while with access to a good chunk of example code and really test it to ensure it's right for you before you have to commit to spending any money. And when you do decide to buy yourself a license, it won't cost you your firstborn son and half your soul either.
The lack of documentation is a little unfortunate, but as this is still pre-1.0, it's not too bad an oversight.
8 of 10 - once it has documentation and native Mac(in development) & Linux(planned) support, I think this engine will be just about perfect.