The biohazard symbol comes to mind as it is meant to be "memorable but meaningless"[0] as a symbol. I imagine it will be in use a century from now, if not longe

The biohazard symbol comes to mind as it is meant to be "memorable but meaningless"[0] as a symbol. I imagine it will be in use a century from now, if not longer, since it was created specifically to convey a hazardous condition. [0] https://web.archive.org/web/20110716160837/http://www.hms.harvard.edu/orsp/coms/BiosafetyResources/History-of-Biohazard-Symbol.htm https://web.archive.org/web/20110716160837/http://www.hms.ha...