Corporate - contact names
Adding an individual to the database and connecting it via a relationship to the organisation would be the coherent "CiviCRM-way" to do it. You should consider using this approach as a lot of CiviCRM's business logic is focussed around it (e.g. greetings, online forms etc.).

If you still want to stick to an "organizations-only-approach", you could simply add one or more custom fields for organisations and enter all relevant infoamtion (such as first and last name) in those fields.