In certain times and places, at least, bearing a particular coat of arms could kill you. No, really!
As explained in the article "Artificial Arms" by David Gelber of The Time Literary Supplement:
On January 13, 1547, as Henry VIII lay close to death, Henry Howard, Earl of Surrey, was brought to the Guildhall and arraigned for treason. His offence: the misappropriation of the arms of Edward the Confessor, with the intent of disrupting the succession and depriving the King's son and lawful heir of the throne. It mattered little that the arms the nobleman stood accused of usurping were a fifteenth-century fabrication (it was only a hundred years after the sainted King's death that the first examples of heraldry appeared). The discovery in the earl's house at Kenninghall of escutcheons of the Confessor's apocryphal arms provided the cabal led by Thomas and Edward Seymour, uncles to the future Edward VI, with the evidence it needed to eliminate a putative enemy. Surrey himself conspired in the fiction that fixed his doom. Far from protesting that the arms were merely a chronicler's invention, he insisted on his family's immortal right to them by gift of King Edward [the Confessor, not Edward Tudor, soon to be Edward VI] himself. These arguments made little impression. A common jury, swayed by the insistence of - among others - Edward Barker, Garter King of Arms, that Surrey had no claim to the arms in question, found him guilty of treason. Six days later he was beheaded.
So be very careful about which emblems you display on your coat of arms if the current monarch is a bit paranoid about his status because he's only the second generation of his family to sit on the throne, and has a tendency to overreact to any threats, real or only perceived, to that status. You have been warned!
The rest of this very readable article describes in narrative form many of the chapters by different authors in the book I spoke of once again in my last post, Heralds and Heraldry in Shakespeare's England, edited by Nigel Ramsay.
The entire article is well worth the read, and if it piques your interest sufficiently to go out and obtain a copy of the full book yourself, well, then, my work here is done.
Mr. Gelber's article can be found on the website of The Times Literary Supplement at http://www.the-tls.co.uk/tls/public/article1509415.ece