I've been slowly watching Durarara the past weeks, I'm around episode 7, slow I know. I was planning on getting through it faster, but then I decided to watch RailGun after seeing Index long ago. All because of the Anime 2013 Battle thread on Crunchyroll.
RailGun first season is pretty generic, with an overload of cuteness and girls that are amazingly fun to watch, but I heard the second season is really really good with the Sisters Arc.