Thinking seriously about using Phaser. I've completed a Ludum Dare jam using it successfully and Unity seems like trouble/overkill.
But that's a lot more programming than Game Maker. I'm also a fan of Game Maker.
Phaser turned out less than ideal. The actual Phaser team did a 32x32 entry last time and by their own admission it was hacky and there's no better way to do it. Love Phaser, but it will be for another day.