Prophet Muhammad (peace be upon him)
The Imam.
By the way they are not called 'Islams' they are called Muslims .There is not really a leader for Muslims. Muslims' God is called Allah which is Arabic for God. Prophet Mohammed is the last prophet and is the leader of the prophets. He is a wonderful role-model to all Muslims. Their book (when i say this i mean religious book, like the Bible) is called the Qur'an which is like a guide sent from Allah to Prophet Mohammed.
He influenced Islam by being it's leader and teacher. Muhammad is regarded as Islams last and final prophet of Allah (God). His religious influence mainly grew by political and military force. Many lands were conquered by military and was converted to follow the religion of Mohammed.
Christmas is a Christian religious celebration, so I doubt it is celebrated by the Islamic religion.
Umar (omar)
zoroaster was a persian religious leader
Judaism has not had one central religious leader in almost 2,000 years.
Peter Spencer - religious leader - was born in 1782.
Peter Spencer - religious leader - died in 1843.
zoroaster was a persian religious leader
Buddhism has many sects and schools and so there is no single religious leader. Much as the pope may be regarded as a Christian leader, he is not the leader of all Christians.
kabir