I haven't collected anything crazy. But I have all my textbooks with me. Right from the 3rd standard upto the end of 4th year of my B.tech, I haven't sold any books like most of my classmates used to do. I covered them all inside the sack and kept on the shelves in my home.
Whenever I feel like I shouldn't have grown up, I simply go through my childhood handwritings and indulge in nostalgia!