After voting in the poll, feel free to explain why you are most fascinated in either ancient, medieval, early modern, or modern history. Personally I am most fascinated in ancient history, because it is the most far removed from our modern world. Ancient Egypt and Mesopotamian Sumer ruled over much of civilization during the early Bronze Age, and by the Iron Age we had Archaic and Classical Greece colonizing virtually the entire Mediterranean and Black Sea regions. The Roman Republic soon dominated the Mediterranean arena and its successor the Roman Empire encompassed so many different territories that now make up a myriad of modern nations in Europe, North Africa, and West Asia.
Meanwhile, the Qin Dynasty of China unified the Warring States, extended the Great Wall, built the Terracotta Army and tumulus for its first emperor, and collapsed during a rebellion that would lead to the establishment of the Han Dynasty of China. The latter was mostly contiguous and contained within the boundaries of modern China (although branching out into what is now North Korea and northern Vietnam); its collapse into the Three Kingdoms of Wei, Wu, and Shu mirrored the Crisis of the Third Century in Rome and China's reunification by the Western Jin Dynasty that of Aurelian's reuniting of the Roman Empire (split into the Gallic and Palmyrene empires). The Mauryan Empire, Kushan Empire, and Gupta Empire of South Asia encompassed much of Pakistan and India, while the Achaemenid, Seleucid, Parthian, and Sasanian empires ruled over a united Persia and Mesopotamia. The Olmecs of Mesoamerica (i.e. Mexico) built a civilization that would serve as a foundation for later ones in the region such as the Mayans and Aztecs. Northeast Africa saw the rise of both the Sudanese Kingdom of Kush and Ethiopian Kingdom of Aksum.
If I had to pick a second favorite it would be the medieval period, since it represents an odd transitional phase in which some of our present-day nation states had their nascent beginnings, such as in the Kingdom of France, Kingdom of England (combined with Wales), Kingdom of Portugal, Kingdom of Denmark, etc. It was also the era of the rise of the Islamic caliphates, the Carolingian Empire, the Crusades, the Mongol Empire and travels of Marco Polo, the infamous Black Death, and the beginnings of gunpowder warfare in Song-dynasty China. It also saw the development of medieval republics from Novgorod to Venice, and the birth of the Renaissance in Italy. It contained both the Islamic toppling of Visigothic Spain and the Spanish Reconquista that drove the Moors into Granada, which finally fell to the Spanish in 1492 at the onset of Columbus' discovery of the Americas. It was also the era of brutal tyrants such as Vlad the Impaler and Timur the Lame, and epic conflicts such as the Hundred Years War.
I suspect some will choose early modern history as their favorite thanks to the Age of Sail, Age of Exploration, the Columbian Exchange and beginnings of globalism, the primacy and waning of the Spanish and Portuguese empires, the building of the British Empire, the European interactions with Ming China and Sengoku/Tokugawa Japan, the European wars of religion, rise of the Dutch Republic, Oliver Cromwell and the English Commonwealth, the Spanish conquest of the Aztecs and Incas, the expansion and decline of the Ottoman Empire, the expansion and decline of the Mughal Empire, the conquest of Ming China by the Manchu Qing Dynasty, the Golden Age of Piracy, the American Revolution, the French Revolution, and the start of Napoleonic age.
I could be wrong, but I think only a handful of you will pick modern history, and only because of World War I and World War II, if not the previous 19th century conflicts such as the Franco-Prussian War and such. Or perhaps I'm wrong...perhaps there are a great many fans of the American Wild West, the Industrial Revolution, the collapse of colonialism, communist revolutions, the Soviet Union and Cold War, the advances in science with works by Charles Darwin and Louis Pasteur, the radically progressive technological innovations before and after the world wars, the creation of so many new genres of music over the course of the 20th century (ragtime, blues, jazz, rock, R&B, soul, funk, disco, hip hop, punk rock, heavy metal, thrash metal, death metal, techno, house music, etc.), and, of course, the rise of Justin Bieber.