Those all create one-word domains from a root word, either dictionary words or semi-dictionary words. Then there are numbers like 360 and 888.
What about add-on words that are not strictly grammatical suffixes, maybe even abbreviations? The one I often see are inc and co, then stuff like group which strictly speaking is a separate word.
Looking at this differently, if a bare keyword was taken, singular and plural, but you could add any suffix or word to it, what would you add?