Almost everyone coins or uses expressions that make sense to only a few people. What word or phrase do you use most often that you have to explain the meaning of to others?
Then I have a whole bunch of made-up words I use as exclamations. I love coming up with new ones, too. :-)
My mother has a whole bevy of unusual phrases that I have borrowed, most of which she got from *her* mom. Like "You're breathing a scab on the end of your nose" is similar in meaning to "Any more cheek outta you and I'll punch you," but Mom always meant it jokingly, she never used it when she was truly angry.
Another momism is "Eat [your vegetables/some other food], it'll grow hair on your toes." Which was not her most effective means of getting us to eat things. She is also fond of breaking out into song at a moment's notice, but usually it's just little snippets, since she doesn't know many of the words to any of those songs.
Then of course, being a writer who loves languages, linguistics, and words in general - and is also an amateur philosopher - I make up all kinds of words for various reasons, often punny words, as I love puns. I even have an entire language all my own, Trai'pahg'nan'nog; it is one of several, and is the most well-developed.
And, just like ysabetwordsmith, I often use nonstandard sounds like animal sounds. I often growl, hiss, purr, chuff out air, audibly sniff at interesting smells, and even occasionally bark for various reasons. I once, out of irritation at a barking dog outside the library, barked back at him/her, and got some funny looks from it. :-)
Lilla, my room mate, also purrs a lot. A lot more than I do, even. And she meows, too. She is fluent in cat language, and can have entire conversations with her cat; she can always tell what his meow is saying.
When I was a kid, I made a HUGE assortment of what my mom called "mouth noises" to add sound effects to make my fantasy world feel more real to me. It drove my parents (and eventually my sister) bonkers, and got me weird looks and worse from kids at school. I can still make all the same sounds, but I generally don't anymore, with the exceptions listed above.
The first time I tried purring for Lilla's cat, Magellan, it came out like a lion's purr and scared the poor cat into running under the bed. I could tell he was saying "BIG KITTY! BIG SCARY KITTY!" in cat language. :-)
I also have been working on, but not having a lot of luck with, a constructed language for an alien race that have an extra set of vocal cords and make a lot of nonstandard language sounds; chirps, whistles, and so on. Although now that I think of it, it would be impossible for humans to speak such a language due to their extra vocal cords. No wonder I'm not having much luck with it!