I'd like to request that the Energy Heart from the Beginner's Box - GM Guide be added either to the regular magic item list or by using the Beginner Box as a source. Its a unique item that grants energy resists to the player carrying it. I'm pretty sure all the rest of the Beginner Box content is covered in the regular Pathfinder Player's Guide and Gamemaster Guide.
As it appears in the GM Guide (can be confirmed via a quick google of the source name, there are like 5 free pdfs out there):
The first time each day that you take acid, cold, electricity, or fire damage, the gem reduces the amount by 10 points (minimum damage is 0).