This is a great question. Hannibal was the son of Hamilcar Barca and lived from 247 -183 BC. He was the greatest Carthaginian general and the fiercest foe that Rome has arguably ever faced, at least during the Republic.
He is best known for his daring attack on the Romans on their soil. He marched an army, which also included elephants, over the Pyrenees into Northern Italy. What was more impressive though was his defeat of several Roman consular armies. He defeated the Romans on three occasions at Trebia, Trasimene, and Cannae. The last of these was a devastating blow, which the Romans never forgot.
In addition, to these victories, Hannibal was able to gain local support to further threaten the Romans. In short, Hannibal nearly became master of Rome.
He is also known for a famous oath that he made as a boy always to be an enemy of Rome. One source reports that Hannibal told his father, "I swear so soon as I am old enough...I will use fire and steel to destory the destiny of Rome."
Fortunately for Rome, Hannibal was defeated by Scipio Africanus at the Battle of Zama.
Hannibal (247–183 or 182 B.C.) was an African ruler who rose to power after a career as one of the world's greatest military commanders. He was born in Carthage, an ancient city on the northern shore of Africa in present-day Tunisia. Gaining the rank of general at age twenty-five, he led African armies against the Romans in the Second Punic War (218–201 B.C.). He ultimately conquered parts of Spain and Italy and nearly defeated the Roman Empire. Hannibal was known for his daring military tactics. During an invasion of Italy he led a small army of select troops on a little-known route over the Pyrennes Mountains and up the Rhône River valley. He then crossed the Alps with elephants and a full baggage train, accomplishing one of the most famous feats in military history. The entire time he skillfully avoided the Roman army, launching a surprise attack and conquering northern Italy. Hannibal was finally defeated by the Romans in Africa in 201, thus ending the Second Punic War. He then became a chief magistrate (administrative judge) of Carthage. He reformed the government and managed to repay the heavy tributes (payments) required by Rome at the end of the war. In 195, when he was accused of conspiring against the Romans, he fled to Syria. He took part in the Syrians' war with Rome, then went to Bithnyia after the Syrians were defeated. Hannibal poisoned himself upon hearing reports that he was about to be turned over to the Romans.
Further Information: Green Robert. Hannibal. New York: Franklin Watts, 1996; Halsall, Paul, ed. Internet Ancient History Sourcebook. [Online] Available http://www.fordham.edu/halsall/ancient/asbook.html, December 20, 1999; "Hannibal." MSN Encarta. [Online] Available http://encarta.msn.com/find/Concise.asp?ti=05A54000, October 16, 2000; Nardo, Don. The Battle of Zama. San Diego: Lucent, 1996; Nardo, Don. The Punic Wars. San Diego: Lucent, 1996.