Star Jelly

Phenomenon of star jelly, a gelatinous substance found on grass or tree branches, often linked to meteor showers in folklore. Described as translucent or grayish-white, it is said to evaporate soon after appearing. Read more in this Wikipedia article.
#6 Actually a really cool list
#19 I remember when I first found out that the Roman statues used to be paint to make them appear lifelike. Creepy.