What about the fusions between japanese and english?
There are lots and lots songs out there that have some english words/sentences/parts in it. Dunno, like Slayers or Detective Conan for example. ^-^ even if it is sometimes difficult to find out what they're singing...
hehe, .hack//SIGN is special. There is not only an english opening, they've got other languages too. I was really surprised to hear "Das Wandern" which is in german (so I had some fun figuring it out
)