I don't know about many statements that need manual ordering, but one without any clear and concise ordering is d:authors of articles used as references. Often there are some reasoning behind who's first (real authors) and who's last (honorables) in the list of authors, but that reasoning is not usually visible anywhere.
We could perhaps add a generic index, but that would be pretty awkward.
Adding this for Wikidata, there are way to many tags for Wikibase… Someone find the right tag!