this topic has come up here at least once before (see ancien regime); but that pointed to words such as: and, the, you, and so on. but what about the most common Nouns?
before you read on, take a shot at this, or at least try to think of some categories.

according to the (probably dated) American Heritage Word Frequency Book the five most common nouns in English are: time, people, way, water, and words. a couple of observations: time, people and words ring true -- I don't get the same feeling with water and certainly no way; and what's surprising is that these are in the main such abstract terms.