Any word or grammatical construction that is criticized is a candidate for citing. Every word that has a usage note in the Random House Webster's College Dictionary can be considered. Any example where a writer explicitly makes a comment about a word, whether it is to dismiss a disliked usage or to dismiss criticism of a usage, is highly valued. Rare or unusual words. Even if a word is already included in one of our dictionaries, if it is relatively uncommon we would like to continue to collect evidence for it.
Words qua words.
Any discussion of a word as such should be cited, whether the writer is talking about how interesting he or she finds it, makes a comment about dating or etymology, discusses its usage, or the like. Words in unusually discordant sources. This will encompass words from the other categories.