Crystal, Santiam, Sterling are some of my favorite hop varieties to use. Great US hybridized version of classic noble hops.
Crystal, a hybridized hallertau variant, has most of the classic Hallertau (mittlefruh) characteristics but to a slightly higher degree, plus a splash of american citrus/lemon character. I have used it from cream ales and blondes to pale ales and IPAs, all the way to amber lagers and light lagers. It's an extremely versatile variety IMO. I have grown particularly fond of it in cream ales, but it works equally as well in the other styles I mentioned.
Have fun with it and toss some in here and there. It's not in-your-face and serves well as a nuance hop.