Anna Dressed in Blood by Kendare Blake
As far as recent young adult horror goes, there isn't much bigger than Anna Dressed in Blood. Kendare Blake mixes ghostly paranormal fantasy and somewhat dark YA horror to create a really remarkable novel. It has won some pretty big awards, and was on NPR's top 5 list for teen books in 2011.
Scare Factor: 3 - It is meant for young adults so it is suitable for everybody, but it can be pretty bloody for YA!