One souvenir that I did bring back however, was a goshuincho, translated into honorable red stamp book. It's used to collect stamps/calligraphy from each shrine or temple you visit. Costs around 300 yen for each stamp.
It was a nice way to document each shrine and temple visit and it was fun to see the different calligraphy styles from each location. It's a unique souvenir which I hope to fill up with more stamps the next time I visit Japan.