This is the most awesome thing I've seen here in a while. I'm in serious danger of blowing off the rest of my day to make a video game to stick these into.
This looks like a great implementation of the sfxr tool that's been around for a long time. I've seen it in Flash and there's an EXE version too. This one has some nice new add-ons I haven't seen yet, and a GREAT interface.
If you REALLY want to go nuts, here is a massive list of indie game development tools that can keep you busy for a while:
http://www.mangatutorials.com/forum/showthread.php?742-The-U...
Seriously, as someone that works with sound and software synths a lot, it looks awful to me. What is it that you like about this?