GameStudio A7 is mature, stable and complete game development solution, powered by -C like- Atari Lite-C language. Suite includes not-so-fancy model editor for creating and importing models, a world editor creating levels, and a full featured Script Editor with highlighting for Lite-C and HLSL, and command help. Features the Acknex 7 engine, an engine using Directx 9 for graphics with full shader support, ODE physics engine, particle emitters, complete multiplayer capabilities and plugin support. Comes in variety of licensing options, all royalty-free including the free version.
Great and easy to use engine that is usually undervalued.
Its easy scripting language is perfect for beginners. Comes with good and solid documentation.
If you ever need help you'll find it in the community forum at the official homepage.