1) tickets for concerts I've been to (going back to the early 70s)
2) vinyl LPs - I have about 900 (started in 1969)
3) CDs - I have about 700
4) DVDs
5) hardcover books
My wife hates me collecting things. If she had her way, she would throw all of it away. Wouldn't even try selling them, or giving them away to interested people. No, just toss the lot into a bin (well, several bins!).