Most of my photography is done using a camera suspended from a kite line. As a result I don't have much of a guarantee that my horizon is level. I used a 4x5 view camera for years before getting into digital and kite aerial photography, so horizon obsession is a way of life. Must level the horizon!
Other than that, I'll occasionally mess with contrast masks to try to recover highlights and shadows. But increasingly I'm making RAW files so I do that recovery during RAW processing.
Past that I don't like to mess with them too much, particularly if a photograph is going to be printed. It's easy to over-process to the point that it can't be printed well, if at all.