This (http://www.youtube.com/watch?v=6yHJDa6NyyM), as uncreative as it is, is the main one. English lyrics are in the commentbox, derp. :V It's a lot more fitting than most anime themes are to the series/characters, so that's the song I always think of if I need music for Fate.

I also have some other non-Nanoha music, but that's just mood music for certain posts and stuff.