Need suggestions on the places to visit in India?

India is a rich country and I would be soon visiting the place with my friends. I have sorted out the places that would be on my top list. But, as we do not have all the time in the world so we have to shortlist some really good places to make our trip. The agenda for the visit would be some real good places that have a mark of history and cultural heritage. We do have our interests in such fields and would like to have some suggestions on that.