One word or rather acronym springs to mind.....FOD.
Crap on the flight deck represents a major flight safety issue. If your aircraft has mechanical linkages your in double trouble. It's all to easy for something to slip under the control coloumn gator into the bell crank...well you see where I'm going and it has happend !
When I was a lad I was taught religously to EMPTY your pockets before entering a flight deck or cockpit.
Even if your in a Scarebus, it runs on wigglies and metal objects in particular represent a high risk when loose in the cockpit. Gum wrappers are perfect for shorting out electrical connections, as are coins.
Gentlemen in the interests of flight safety please keep your work area not just clean but immaculate.
As an aside
Standard practice for fastjet crew to do
FOD checks usually a period of inverted fligth does the trick, the length of which is governed by how much stuff the crew pick off the canopy.