Where is the best place I can sell my used games at a fair price?

Well, I bought Black Ops when it came out, and when I heard rumors about Modern Warfare 3 and Battlefield 3 coming out, I wanna sell Black Ops. I bought it @ Best Buy. Though, I don't want to give them my game back since it's opened. I don't know if game stop is even good. Oh and I live over at Reno, NV so, if I don't know what store your talking about, oh well. Haha. Anyway's, anywhere good and actually have good deals for me?