[ClimaxGravely]

Sorry I should have done that from the first place.

Here's a quick one as I'm on a movie break. I'll make a note to update this in the morning.

Haxe + Haxeflixel : pixel art games

Haxe + Heaps : More general 2d/3d framework with webgl target

Godot : I havent used it personally but I've had a myriad of co-workers tell me how good it is

Monogame/FNA : Open source multi-target C# framework that more or less fits the XNA api. I love this one. Might be really good for C# programmers.

[ClimaxGravely]

To add to this, some people I've worked with are talking about the stride engine (formally known as Xenko). MIT/C# engine