When lasered, PVC heats up and releases a vapor that contains chlorine gas. The chlorine gas released is not only dangerous to you, but it is also corrosive, damages your machine, and voids your warranty. I have seen folks post about making custom holsters from Kydex and that they are engraved and cut on a laser; as a warning, Kydex also contains PVC (again, check the MSDS sheet) and is dangerous to process.
-Braden Todd, Glassmith2