One thing I love about working in a public library is the variety of enquiries you deal with. Family and local history, academic, medical, historical, literature, sporting, geographical, technical, legal, scientific, crossword clues... you never know what's coming next.
My favourite enquiries are the ones where I have to do a bit of digging - where it's not just a matter of looking things up on Wikipedia or Google. Especially when the enquirer doesn't have all the information, only clues. I had one yesterday after a book - he knew the author, and that it was 'something to do with a theory of imagination'. It took a few minutes, but I found the reader his book (as per Ranganathan's 2nd Law of Librarianship).
I had another fun little fact-finding mission the other day. I had an enquirer on the phone asking vague questions about local newspapers from February 1940, which we have on microfilm. He wanted a physical copy, which would be much harder to find (probably something for the county archives), but we can print out articles from our microfilm readers. It transpired that wanted to get hold of an old newspaper to give to his friend as a 75th birthday present. So I told him I would call him back and spent the next few hours researching.
Unfortunately I could not find physical copies of the local paper for sale anywhere (there were a number of national ones) and the local paper themselves only have archives going back a few years. I did find a digital copy of the edition he was looking for on the British Newspaper Archive website, and was able to download the edition page by page. (While looking through the paper, I found a great 1940 crossword with clues like 'A girl's name', 'A bird' and 'A wriggly fish' - that kept me entertained for 10 minutes.)
I compiled all the individual pages into a single .pdf document, then called him back to let him know how I had progressed. He was very grateful and apologised for all the work he'd put me through.
'I enjoyed doing the research,' I told him.
'I bet you did!' he replied.