Not a citation guide, but a writing guide for journalists from the Associated Press. Provides "guidelines for spelling, language, punctuation, usage and journalistic style."
Quick guide from Scientific Style and Formatting (8th ed.), the official manual of the Council of Science Editors used by many science journals, and the three systems of citation used in CSE journals.
The 2018 editorial style manual of the Institute of Electrical and Electronics Engineers (IEEE), a style commonly used in technical fields like computer science.
The Linguistics Society of America's Unified Style Sheet for Linguistics Journals (2003). See also the specific Language Style Sheet used in that journal.