Difficult to narrow it down to just one. My selection would include York and Paddington for sure.
I would also add Pickering as a heritage site, as I've been there many times and has a good atmosphere.
My nearest station is Liverpool Lime Street, which currently undergoing a major face lift (at last!). When completed I think it will look very impressive once again.
How about a nomination for worst station? For me that would have to be Manchester Oxford Road - IMO it's the most depressing station in terms of atmosphere and looks. Plus I've waited for connecting trains freezing cold on it's platforms more times than I care to remember!