In situations where you can't rely on automatic exposure, being comfortable with manual control is a must.
Shooting a waterfall is a great time to use shutter priority mode.
White balance made all the difference in this photo. If it was not on the "cloudy" setting, the image would lose the richness of the sunrise.
In situations with significant portions of the scene in dramatically different light, spot metering allows you to control exposure more effectively than weighted average metering.
Exposure compensation can help you deal with an overload of light in auto modes.
HDR allows photographers to capture a wide array of light without complicated graduated filter systems.