A "special souvenir" refers to a unique item someone keeps to remember a specific place or event that has sentimental value or holds fond memories. Full definition
Pick up locally crafted jewelry or find special souvenirs for your friends back home. (tamarindreefresort.com)
Every single special souvenir... broken to bits, save one from a museum exhibit in London. (littlemisscelebration.com)
«There is still (and probably will be for a while) a market for collectible editions, signed books and other special souvenirs that bring the emotional component of a book to the fore. (virtualdavis.com)