Nelson Mandela was one of them.
As global leaders gathered to pay homage this week to South Africa's anti-apartheid legend who died on Thursday, one former close aide recalled the cheeky lese majeste of a statesmen who charmed enemies, celebrities and ordinary people alike.
"When he paid visits to Queen Elizabeth, it was always very entertaining to see their interaction, because he called her 'Elizabeth'...no one else in the world, I think, calls her 'Elizabeth'," Zelda la Grange, who was Mandela's personal assistant for more than a decade, told Reuters.
"He would comment on her dress and her weight, you don't do that with the Queen," said la Grange, who accompanied Mandela on his trips and meetings with foreign leaders.
Far from being offended, la Grange recalled, the British sovereign "quite enjoyed it".
"She really adored him," she added.
Queen Elizabeth will not be attending the state funeral for Mandela scheduled for next Sunday at his ancestral home of Qunu in the Eastern Cape, but she will be represented by her son, Prince Charles, the Prince of Wales.
(Reporting by Pascal Fletcher and Shafiek Tassiem; Editing by Angus MacSwan)