The hardest part is picking fandoms. I had to reach back to my adolescence - makes me feel young. Of course I skipped over many stories I consider myself fannish about. I couldn't make them work for various reasons: no specific favorite character, too few characters, fandom actually involves actual human beings and not fictional characters, etc. Also, the whole shared universe aspect was at times confusing to my poor little brain.
But I thought of enough fandoms and characters. Here is my list, in no particular order:
1. BtVS: Buffy Summers
2. Torchwood: Dr. Owen Harper
3. Supernatural: Sam Winchester
4. Jessica Jones: Jessica Jones
5. Runaways: Karolina Dean
6. The Riddlemaster Trilogy: Deth
7. The Vampire Diaries: Anna
8. The West Wing: Leo McGarry
9. The Lord of the Rings: Pippin
10. Spider-Man comics: Mary Jane Watson