One of the most inappropriate things you can do at work is clip your nails. And I've had two jobs now where people do just that. At my old law firm, my partner used to clip his finger nails during conference calls; and now at my current job a guy clips his finger nails at random times. At least my old partner had an office and clipped in his office--not everyone heard it. But at my current job, the guy clips his nails in the open. All of the people working in the cubicles can hear him and I can hear him across the hall in my office.
When I lived in New York and rode the subway, I occasionally saw people on the subway clipping their finger nails. That was totally unacceptable behavior; we were on public transportation. But people still did it. And people are going to continue to clip their nails at work even though I personally feel that nail clipping is an at home (possibly even only for the bathroom) private activity. That sound--it just icks me out.