The most world-class game engine to date, Unreal Engine 4 gives you the power to do more than ever before. Bring your creative visions to life directly in game without programmer assistance via the new Blueprint.
I could go on and on about how much I enjoy working with UE4. Of all the game engines I have tried and worked with this one is truly the one I like the most. And the fact that it is free* is amazing. I would definitely recommend this to people if they didn't already know about it...
Unreal Engine 4 is an intuitive, and advanced in both graphical and workflow perspectives. I started using UE4 a few months back, and it's been a smooth ride so far with the exceptions of frequent crashes due to the instability of 4.8.x, which is also the reason for 9 instead of 10.
Runs on multiple Operating systems, Can develop for all major platforms. is artist and programer friendly, Full access to source code if needed or projects can be done entirely in Blueprint, a node based visual scripting environment that is great for projects that only have technical artist and designers.