While we offer 13 categories of ethical dilemmas, there are thousands of ways these manifest themselves in the real world.
As a case in point, take a moment to skim the Department of Defense's Encyclopedia of Ethical Failure. (The link is to a Word document.) Here, the DoD documents many of the ethical failures it's seen over the years as a caution to all of its personnel and contractors.
Perhaps one of the most entertaining entries:
An offshore safety inspector found much of the Government’s equipment to be in need of repairs to meet safety standards. He then referred the business to his brother-in-law's repair shop. The rig operators smelled a rat and called the FBI. They discovered that, in return for each referral, the brother-in-law was treating the inspector to an evening with a lady of dubious morals.
The case was brought to trial. In his defense, the inspector claimed that he had not received a "thing of value" in return for the referral. The judge didn't buy it - and neither did his wife.