Maxximum, my personal favorite game maker is megazeux, which is rather archaic but also rather... well, you can do a lot with it if you try. The main and glaring limitation is the visuals, which are limited to 2 color editted ascii characters (although you can make them four colors if your want using... some... different rendering mode although only one guy from Quebec was ever really good at it from what I remember).
VERGE is another option if you want something really geared towards RPGs, I guess? No idea how developed it really ever got.
Game Maker and Constructs are other big ones. Construct is totally free but apparently might still have some weird glitches.
Lots of people use Flixel with some kind of freeware flash IDE.
Oh huh, Verge apparently lets you use Lua for scripting. Worth checking out for that, I'd think. Lua's a really nice language. Not quite as awesome as Common Lisp but it's close.