That heinous matt of hair that collects in the drain of your shower making your tub back up and your stomach hurl.
For best results, sneak up on the shower squirrel and plunge your hand without looking, scoop up the offending hair in your clutched fingers and deposit quickly into the awaiting toilet. Make sure to close the lid immediately. Shower squirrels can be resilient little buggers. Flush. Latex gloves are optional.