This is probably always going to be a matter of contention - Australian Prime Ministers are arguably all equally famous (or alternatively, equally unknown), with the exception of perhaps Frank Forde who was Prime Minister for only one week.
The longest-serving Prime Minister of Australia was Sir Robert Menzies, who probably qualifies as one of the more well known ones. Others include Gough Whitlam (the first Labor Prime Minister in 23 years, who was dismissed in sensational circumstances), Alfred Deakin (a long-serving early Prime Minister who was also influential in the Federation movement), Billy Hughes (Prime Minister during World War I), John Curtin (Prime Minister during World War II), Malcolm Fraser, Bob Hawke, Paul Keating, and John Howard (all of whom were recent Prime Ministers, and each of whom is remembered for different contributions that they made to recent Australian history).
Julia Gillard is the most recent Australian Prime Minister.
Prime Minister
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Winston Churchill would be one of the most famous British Prime Ministers.
One of the things Jawaharla Nehru is most famous for is being the very first Prime Minister of India. He also famous for being the father of one of India's most famous Prime Minister, Indira Gandhi.
Sardar Manmohan Singh is the famous prime minister of India.
Are you asking about the government structure such as a prime minister or about the Australian army? Here's a link for the Australian army ranks: http://en.wikipedia.org/wiki/Australian_Army_officer_rank_insignia
Stanley Bruce was Prime Minister in Australia for most of 1929 - up until 12 October 1929. James Scullin then served as Prime Minister through to 19 December 1931.
Members of the Australian Parliament and Senate are elected by the people. The leader of the political party with the most elected members becomes the Prime Minister.
Mahatma Ghandi is the most famous person with the name Ghandi. Indira Ghandi was the third prime minister of India. She was assassinated. She was the second longest serving prime minister of India.
One of the things Jawaharla Nehru is most famous for is being the very first Prime Minister of India. He also famous for being the father of one of India's most famous Prime Minister, Indira Gandhi.
Pierre Elliott Trudeau. He is no longer the Prime Minister of Canada, but is one of the most famous ones. He passed away a few years ago.