Stencyl, which I use, is a powerful, game creating tool. You can make games, sprites, scripts and export them to StencylForge, where they will be used and modified by other users and eventually become part of something awesome. It's 100% free, too. Here is where you ask for help with the simplistic but flexible block-script (you can also use ActionScript) or for collisions or anything else Stencyl-y. Ever play Balls in Space? Stencyl. SkullFace? That's right. Stencyl. Anyway, this is where you ask for help with Stencyl.