I usually tend toward a nice curly maple and figured walnut (or burl), but really anything curly and burly looks beautiful. I've recently started working with quarter sawn sycamore and it's really nice.
You can also take a curly or figured maple and stain it to a darker color and it will really bring out the grain. Check out Kenny M's website for a really nice picture of a stained figured maple bow. Beautiful.
Joe