Love2D
Looks interesting! I've heard of this engine before but have been warned that the community/documentation is a little immature. This doesn't really bother me too much and I'm interested in trying out Lua, so I'll probably check this out! Have you used Love for any games? Have you had any issues with the engine at all?
Huh. Maybe that was an older opinion? I would have said that Love has some of the best documentation I've ever seen. Sometimes things aren't cross-referenced quite as well as they could be, but I've only found one major omission that I can think of (the foreground color is used as the "tint" and global alpha for drawing images, which is hinted at under
setColor but not mentioned on the page for
draw. It's certainly not as bad as Unity's documentation. And of course Lua is quite well documented.
The Love community is definitely small and has a lot of complete beginners, but there are a few people who know their stuff.
The engine itself is pretty nice. The documentation shows which versions added and removed various bits of functionality, and it's clear that they have steadily cleaned up the APIs and made them simpler and more powerful. I've been pretty impressed with it. As with LibGDX, SFML, and SDL, it's more on the "toolkit" end of things than the "complete engine" end of things. It doesn't have game objects that move themselves or anything like that: it just gives you global
update and
draw callbacks. It's more-or-less a Lua wrapper for SDL with a simple main loop and a 2D renderer built on OpenGL. There's no editor (in fact the community seems to be against general-purpose game/level editors). It has Box2D built-in for physics. If you want simpler collision detection there's nothing built-in, but there are a number of Lua libraries you can download.
A lot of 2D games these days are going with 3D rendering. If you might go in that direction, or want an editor, or want a more complete engine with built-in objects and scenes and such, I'd try Defold.