The fullmoon in most stories. It is during the brightest phase of the moon that bad things happen in media, especially when it has to do with werewolves. This might have a natural origin in that people might get more naturally anxious during bright moon phases, as during the night predators lurk and a source of light only allows them to see you better.
Doubles as Dark is Not Evil because only the bright full moon is seen as evil, while the dark new moon is generally good (or neutral).
In documentaries and deserts, drought is usually accompanied by shots of the sun and its white midday glare.
Absolutely ubiquitous in propaganda campaigns. You'd be hard pressed to find a totalitarian regime that hasn't accompanied its brutal repression or wars of aggression with colourful posters of smiling babies and clear blue skies and healthy, hard-working, and attractive young mothers, students, farmers, and soldiers striving for a Brighter Tomorrow.