Well, Snape's in my top four of favorite characters so I'm probably bias- Neh, I don't do biased.
Snape... Well, I loved him for his humor and how he was always so mysterious and we were never really sure if he was the good or the bad guy. And then they revealed his love for Lily Evans which cleared up an unreasonable amount of things. It's a sad history but I can't believe he actually held on to that love for one person his entire life. That, I think, is really, terribly sad. I wish JK hadn't killed him off because as a man he had much more potential than teaching little 'dunderheads' and perhaps, after Voldy was dead and Dumbledore was dead (may he rest in peace) he could've finally actually moved on, ya know?
That and he should hook up with Granger and conquer the academical world with her after she ditched Ron Weasley.