I was surprised to not see Clickteam Fusion here. Hundreds of games have been made in Fusion including big ones like Knytt Underground. It has been around in its various incarnations for almost two decades and is still going strong. It's the engine that Construct directly ripped off (apparently Scirra have even forced their way into Clickteam conventions before trying to market Construct).
Fusion is very accessible to beginners, however as a game industry veteran knowing dozens of languages and engines, I still use Fusion all the time! Almost all the games on my website were made in it. It's deceptively powerful as its mouse-based scripting language lets you lay down the logic for a game much, much faster than in traditional languages. I know Unity inside and out but I can probably make a 2D game around 3-4 times faster in Fusion (no joke).