Without wanting to sound rude, there are a variety of really good guide books and travel sites, including this one, that list all the major and minor attractions in every country. It would be a better idea for you to visit those first and then come back with specific questions that experienced travellers can help you with.
I could list off a whole range of tourist sites, the Taj Mahal, the temples of Kajuraho, the Ajanta caves, Jaisalmer …But it would all be absolutely worthless unless I know a little more about you, your interests, what would you like to see? What would you like to do? Are you alone or with children by the tag on your question?