Literally any situation where someone has lied can work. Situations where you had to choose between helping one person over another. Situations where something you wanted to do went against what others wanted you to do. You can twist almost anything into an ethical dilemma if you put it in the proper context. Example: I felt like I needed to poop really badly but had a patient who I just found out needed to be seen several hours ago and is becoming agitated and making inappropriate statements towards staff about not being seen. Do I go to and see the patient now, knowing that I'll be distracted during the interview and possibly not provide the best care because of my discomfort or do I go to the bathroom so I can give the patient my full, undivided attention and risk the patient becoming agitated and lashing out in a more aggressive way? Not a real situation, but just showing how you can turn a ridiculous example into an ethical dilemma.
I hated these kind of questions because you never know what the person asking wants. Some just want to know you think about things every so often and that you show decent judgment. Others want you to give a home-run answer about a real, major dilemma you faced. It's not really fair as what consists of a "good" answer is extremely subjective based on the interviewer.