In my experience, I cannot think of an example of when it is a good idea to talk to the police without a lawyer.
Clients have approached me in the past because they have received a phone call from the police looking to speak with them. Chances are they were trying to press charges but did not have enough evidence yet to do so.
Speaking with the police and admitting facts that gives them enough reason to charge you is a bad idea. Now they have your admission to use against you to press charges and the admission can be used against you in court as well.
Never forget that you have a Fifth Amendment right against self-incrimination. You also have the right to have an attorney present during police interviews. In some circumstances, an attorney can help avoid charges being filed against you to being with.
If the police are looking to speak with you or even if charges have already been filed against you, it is critical that you speak with an attorney as soon as possible.