Panda.js looks like a neat JS Game Engine featuring a Canvas/WebGL Renderer, Physics engine, Particle engine, Tweening, Sound Manager, etc. It also plays nice with mobile/touch interfaces. Example game is this neat Flappybird clone, Flying Dog.
Panda.js HTML5 game engine →
Flying Dog Source (GitHub) →
Related: Be sure to check out Vladibird, an altered version of Flying Dog where you have to fly Vladimir Putin between pillars of asses.