VoidTools' Everything. Indexes your whole filesystem (across all drives too) and allows you to search your whole filesystem for matching filenames, save search presets for later, and even allowing RegEx search queries if you need files of names matching some pattern.
No, I mean you can search for the contents of text files, like PDFs, DOCX, TXT, etc. not only the file names. Sometimes you know what you read but don't know the name of the file and in this case you can look for what you remember and find your file this way.
Another pro for everything is that you can index remote storage as well, you can't do that with the windows provided indexing. I use this a lot for work, since I usually do not have the patience to look through the file structure of our server to find something.