This question falls under the identification of both a "throughout history" question and a "poll-type" question, and has been removed as a result.

I would start with Alexander the Great, seems to be a good beginning in Ancient warfare. If you're already reading about Hannibal, you're bound to run into Scipio Africanus (Roman General who defeated him). Julius Ceasar and Pompey were prominent Roman Generals in the same period. Charlemagne is a good read, and William the Conqueror. Then there's Sir Francis Drake and his defeat of the Spanish Armada for naval warfare. Napoleon is a huge one, the best Commander of his time, but also read about Arthur Wellesley, the Duke of Wellington, who served Napoleon both of his defeats. General Patton is a must for modern warfare, specifically with tanks, and on the flip side of that Erwin Rommel was a terrific General for the Axis, noted for his campaigns in North Africa. General Douglas McArthur as well for his strategic island hopping in the Pacific Theatre.

Obviously this is a very incomplete list, but there's a pretty good start.