I collect:
1. 8/16mm cameras. 18 to date.
8/16/35mm film especially 8mm home videos of birthdays, weddings, vacations etc.
2. Documentaries & films, especially War & Kid films like: Little Criminals, Stand by me, Fresh, Virgin Suicides, Tex, Basketball diaries, Bugsy Malone, Kids, Bully, Ken Park, Pups, River's Edge etc.
3. Water pistols and replica guns in all shapes, colours and sizes.
4. Art
5. Computer viruses (Worms, Trojan horses, Macro's) including the notorious "I love you" one.
Here's is a link to lists of thousands.
Wikipedia
As depicted in Star Trek.