While employed by Sanderson & Grainger, the Eleventh Doctor wore a badge with his name on. As he claimed to Craig Owens, he wore it in case he forgot who he was. (TV: Closing Time)
Giles showed his P.R.O.B.E. badge to get access to Tower Bridge when it was closed off by police and MI5 forces due to the appearance of a rift. (AUDIO: Guardian At The Gate)