Usually, when someone walks up to the desk with something in their hand and asks "can you help me find this," it'll be an easy question. 99 patrons out of 100 will have a piece of paper with a book's title, call number or ISBN written on it.
(In librarianese, this is called a "known-item search" - you know ahead of time exactly which item you're looking for.)
But, lucky me, I met #100.
A woman walked up to the desk and asked "can you help me find this," but she wasn't carrying a piece of paper. She had a little Tupperware container. I knew then that this was definitely an "unknown-item" search.
She took the lid off, and then repeatedly shook it, as if trying to get something inside to turn over. Eventually she righted what was inside, and held it out to me saying, "I found this in my basement and want to know what it is."
What it was was an insect/centipedey thing. About an inch long, light brown, with a lot of very wispy legs, and two long antennae. I was surprised that it had survived the trip and all the shaking, but it was crawling around in there, along with a couple bits of dirt and brick. And she wanted me to help her identify it.
I took her over to the 595's [?], and she started flipping through a few insect encyclopedias. However, not knowing the name of the bug, it became clear that identifying it was going to be tough. I showed her how to use the index to look up centipedes, told her to keep looking, and I went to do some internet searching.
Not knowing what to call this thing, I searched for "bug identification." I was hoping for a website that would guide me through the identification process by asking questions, such as "does it have more than six legs?," "does it have wings?," etc.
But the final website on the first page paid off - Dave's Garden Bug & Insect Identification database. Instead of asking questions, it just had a long list of photographs. These were easy to scan through, and halfway down the page I spotted our quarry: of the family scutigeromorpha, commonly known as house centipedes.
From that, we went back to the book shelf and quickly found a book with a section on them. Granted, the entire search process took more time than it took to read the section, but the patron was happy to know what it was - and that it's pretty harmless.
Unfortunately for this bug, I don't think riding around in a Tupperware container is at all harmless.