Raining Diamonds :
[Neptune and Uranus] contain a high proportion of methane, which UC Berkeley researchers have now shown can turn into diamond at the high temperatures and pressures found inside these planets.
"Once these diamonds form, they fall like raindrops or hailstones toward the center of the planet."
Raining Glass :
[HD 189733b] has molten glass rain that seems to be responsible for the blue marble appearance, and it also has extreme temperatures and winds. ...The temperatures can go up to 2,000 degrees Fahrenheit during the day while the winds can reach 4,500 miles per hour.
Iron Rain :
Intriguingly, the temperature of OGLE-TR-56b’s upper atmosphere is theoretically just right to form clouds, not of water vapor, but of iron atoms. Earlier this year, astronomers reported evidence for iron rain on brown dwarfs. However, such storms only occur over a short portion of a brown dwarf’s lifetime, while the newly discovered 4 billion year-old OGLE-TR-56b should still be experiencing this exotic weather, thanks to strong heating from the nearby star.