Not really in any sort of order and really leaning towards western/European history since I am sadly not very well versed in other areas besides U.S. (basically the baby of it anyway) and starting to get into South-East Asia.
1. Alexander the Great: Pretty obvious here, he destroyed the Persian Empire as it was at the time, and even made it all the way to parts of India where his image was hailed as a great victor. He tried to merge the cultures of Greece and his Persian conquests, and even though it failed Greek culture became huge in the parts of the western known world for centuries. A bit of a tragic figure, but so are a lot of the big figures in history.
2. Archimedes: The man responsible for one of our most hated subjects in school (XD), he was at the forefront of mathematics in antiquity and it was his work that led to calculus, the area of shapes, and various physical tools like the screw named after him and compound levers. His works have had a great effect on the field of math, which is very important...even if we don't like it that much. He even built some sort of heat weapon that supposedly used mirrors to light the sails of the Roman boats attacking Syracuse aflame!
4. Cicero: A great orator, lawyer, politician, and philosopher who tangled with a lot of the big names of the late Roman Republic. He was trained in Greece and brought a lot of their philosophies back to Rome, and after the collapse of the western empire his writings influenced languages and the spread of ideas up to even the age of enlightenment. Also a bit controversial in a few of his actions, but whateva!
5. Augustus: I think that even though his adoptive father Julius Caesar was the one who paved the way for him, it was Augustus who became the first emperor of Rome and influenced it all the way to its end. His military victories, architectural achievements, and forms of propaganda had great effects which turned Rome into the empire that spread itself far and wide after bringing a lot of territory into it.