Using the summon command on Vanilla

/summon ArmorStand ~ ~ ~

{CustomName:Help I cant destroy this,CustomNameVisible:1, Invisible:1}

Creates a nametag which will stay there and cannot be removed. You cannot destroy this by hitting it and the only way to actually get it to remove is to break the block which it is on to make it fall out the world.

You cannot blow it up with TNT.