A little grocery store in Upland , Indiana had a orange/vanilla slushy that was tasty. But they rotate the flavors in their machine, and haven't had it in awhile.
I did like the vanilla/orange coke they had a few years ago, if I chilled it in the freezer for about an hour. If it was merely cool , the orange would be very tart, and you couldn't taste the vanilla. But as it started to freeze and become a little slushy, the combined flavors tasted perfect together.