Remember that file someone sent to you in an email? Archived it and can't remember what it was called?
Go to your webmail view (you DO use webmail, right? It's way faster than your desktop computer's mail application, because nearly ALL of the indexing, storage, and system processing is done in the cloud)
Type "/" to put the cursor in the search area.
Type "has:attachment" and then put whatever other search terms will help limit the results. So if your Mom sent you a turkey recipe as a PDF attachment, you could type "has:attachment thanksgiving" and Google will return messages that only contain the word "thanksgiving" and include file attachment(s) in them.
This is a very handy and deceptively simple tool, one of literally dozens that Gmail makes effortless once you learn the syntax.
BONUS TIP: what about the size of the attachments? You can constrain the search to just a certain size of file!
Add "larger_than:5m smaller_than:8M" to your search to limit to just a specific size of file. Alternatively, you can type "size:5mb" if you know the exact size you're wanting to locate.