City: I don't think there is a city in America whose name hasn't been used in the name of a consulting firm. People use city names because it makes them seem bigger than they are, the name of the city is easily memorable, or the name of the city will show up higher on Internet searches.
County: Consultants who focus on a specific county use the name of the county for the same reasons people choose cities.
Country: The reason a consultant chooses a country is to convey a sense of reach and because the name is usually memorable.
Descriptive: Using a descriptive word tells people what you do.
Full Names: The most famous company I can think of that is based on a full name is JPMorgan, the bank named for the investment banker that is now part of JPMorgan Chase, a combination investment and commercial bank.
Home or Business Address: Some people use their street addresses as their business name. There is a marketing firm in New York called Broadway Associates. The Wall Street Journal chose its name so it would be memorable to the stock traders and investment bankers who populated Wall Street.
Last Names: Use your name if it is well known so that when you walk into a room or speak with people, they can identify you easily. I use my last name in my consulting practice because I ran a large trade association in my region and have served on many regional boards. Some of the greatest business leaders, such as Disney, Ford and Trump, have all used their last names. Be careful if your name is long and unwieldy. You don't want prospective customers to become frustrated because they can't spell your name and therefore can't find you by telephone or on the Internet.
Mythological: There is a German information systems consulting firm that named itself after the Greek god Zeus. Using a mythological name suggests an intellectual foundation.