COMIC BOOKS. COINS. HAND GUNS. Thimbles. Breyer horses. Romantic conquests. Shoes. Recipes. Baseball cards. Tombstone rubbings. Tarot decks. 
Q. What do all these have in common?
A. Someone, somewhere, collects them. (And may occasionally engage in some pretty edgy behaviors in the pursuit.)
Writing prompt
Make a list of collectibles. Then, building on your own experience as a collector, or your observations of a collector in your world, write about a situation (fictional or non) in which a collector of one of the categories on your list goes out on a limb, putting himself—or his loved ones—in jeopardy to acquire a new piece for his collection.
Does he cross the line into hoarding? Mortgage his house or skip the rent to make his purchase? Get out of his depth at an auction? List things that could go wrong. Then put a desired object just out of his reach—and go from there.