Great, man, it seems that you really know what you are doing
This one sounds PERFECT for me. It really has 'the right feeling' for an ambient & spooky atmosphere. Great job !
I already wrote a patch tracker item, so I think you will hear from Mattn soon...
I would use this one for some funky space-alien-machine, but you are the creator of this & I think you should choose where to use it
If you have some other sounds in mind or have seen objects in the game which should have a sound assigned feel free to post those stuff here, I am sure there will soon be also a big revision of the current sound system, because there also has some bugfixing regarding hurtsound to be done...
Greetinx.