When you try to stop yourself from laughing and fail, you make a "chuckle" sound: a stop-like release when the air from your laughter-compressed lungs, prevented from escaping through your mouth, finds a way out through your nose.
These sounds (unvoiced and voiced) could theoretically be used in speech. They would impose severe constraints on adjacent sounds, but so do clicks, and clicks exist. Do chuckles exist?
EDIT: Non-phonemic realizations? Whatcha toQXng'mbout?