11. Search allinurl

allinurl: xxxxxx

The allinurl operator does the same as the inurl operator, but then for multiple search terms.

12. Search filetype

filetype: xxxx

By using the filetype operator you can limit the search to certain document types, such as pdf, doc, ppt etc.
Suppose you are looking for the annual report of a company.
There is a good chance that that annual report will be available as a pdf-file on the website of that company.
Your search can then look like this: company name filetype: pdf

13. Define keyword

define: xxxxxx

With the define operator you ask Google to provide definitions of the specified keyword. So a kind of dictionary.
For example, the search define: affiliate marketing yields the following result:

14. Search related

related: xxxxxx

With the related operator, Google displays related pages from the specified website.
For example: related: https://www.whitehouse.gov/ provides a list of sites from other government ministries

15. Search movie reviews

movie: xxxxx

The movie operator collects English reviews of the given movie. For example: movie: Titanic