A little girl (maybe a fifth grader) came to the reference desk and asked if I could help her find a picture on the internet. She said she had found it at home using Google image search, but their printer is broken. However, now that she's at the library and can print it, she can't find the same picture again.
She was looking for pictures of the characters from the Ivy and Bean books to put in a school report. She couldn't remember her exact search terms, so we first started searching Google with just "ivy and bean."
We looked through the first four or five pages, but she didn't see the pictures she was looking for (drawings of the characters from the stories, and not just the book covers). We then tried a variety of other phrases, like "ivy and bean" pictures, "ivy and bean" annie barrows, and even criss cross applesauce, which apparently is what the character says in one of the pictures she saw.
But after five or ten minutes of trying various keywords, we still had nothing, and my little patron was getting discouraged.
LibrarianInBlack often reminds people not to rely on just one search engine, so I switched over to AllTheWeb's image search. The patron was reluctant, because she knew she had seen them in Google images search, but she went along with it - and we were rewarded quickly.
On the first page of a search for "ivy and bean," we found one of the pictures she had seen. Every search results page after that had additional images, and she got more and more excited with each picture we found.
She wrote down the URL and raced back to the computer she was using - overjoyed to continue with her homework.