Yes, Harry Potter himself was a fan of Severus Snape! 

Alright, so maybe in the books and films it took quite a lot of secrets and quite a few years for Harry to realize what a role Snape played in his life, but all the years back then, when Daniel Radcliffe was a very young Potter, he went to support his Harry Potter co-star Alan Rickman in an unknown play. In the letter, Radcliffe even wished him a "Merry Xmas"! (Gah, how cute!!)

Neil Pearson of Neil Pearson Rare Books obtained quite a collection of Rickman's scripts, letters and photographs amongst which included fanmail not only from Radcliffe, but from various celebrities including Nicole Kidman and David Hare.

Celebrities are human too and it looks like Kidman was a bit shy, but found Rickman's performance inspiring!

According to news from Neil Pearson Rare Books, Rickman's archive will be on sale this spring, which also includes more than just fanmail but annotated scripts, private photos, props, awards, and even personal diaries!