Without question, the biggest anime of the year is Attack on Titan. It is pretty serious action/epic, but if you want to get caught up, that is a must-see.
There are a lot of anime I am currently watching, but they are all relatively new. I can't speak for the whole year, but at least for the season, I'd suggest watching Servant x Service and WataMote, just for a couple. Those are both really funny slice-of-life stories. Probably not gonna be big or cosplayed at Kumoricon, but they're worth watching for sure.