There are two suffixes both spelled -wI'. One is a type 9 verb suffix and means approximately the same thing as the "-er" suffix in English, turning a verb like pe' cut into a noun like pe'wI' cutter. It can be grammatically placed on any verb not already bearing a type 9 suffix. (There's a strong tendency not to use it after too many other suffixes, as most people seem to think it's best used for simple ideas. If you want to say "thing that is apparently ready to resume being red", consider Doqrupqa'law'bogh Doch instead of Doqrupqa'law'wI'.)
The other -wI' is a noun suffix, meaning "my" and applying to nouns referring to beings capable of speech. For example, vav father, vavwI' my father. There is no actual grammatical restriction against using it on other nouns, but doing so might not make sense to the person hearing or reading it.
I can't think of any examples of -wI' added to chuvmey (words that are neither nouns nor verbs), though perhaps the use of ordinal numbers as if they were nouns (e.g. cha'DIchwI' my second) might count.
Thanks for the help. I was talking abou the "-er" one. Sorry for not mentioning that.