On an outcall I sat on the sofa (in stockings) and as I was talking felt something small and sharp digging in my leg, I absent mindedly pulled it out of the sofa, thinking it was a splinter. It was a tiny feather from the stuffing. But he looked at me, mouth open like I'd just committed some atrocity, jumped up and grabbed the feather and made a big scene of putting it on the table. It was all downhill from there. I never heard from him again so he hasn't forgiven me. I'll live.
Another time I grabbed the lube, instead of the 2 in 1 lube/massage gel, and poured it over a client's back during a massage. It made a mess. An awful mess.