The Engine FAQ <- start here
Which HTML5 Game Engine is right for you
GDevelop – Create games without programming
Stencyl: Make games without code
Feeling overwhelmed? Choose Unity.
Twine is an open-source tool for telling interactive, nonlinear stories.
Ren’Py is a visual novel engine
ink – The powerful scripting language behind 80 Days
Phaser – HTML5
PlayCanvas – online engine
SpatialOS is a distributed operating system enabling you to create huge simulations inhabited by millions of complex entities.