Water

Water was a prized liquid for those who lived under the surface on Ravolox. (DW: The Mysterious Planet)

Water was a seen as a source of great wealth for the Martians, On Mars, great warriors were often entombed in blocks of ice. (NA: The Dying Days, BFA: Red Dawn)

On some planets, such as Kar-Charrat, water was a form of sentient life in itself (BFA: The Genocide Machine, DWAN: Pitter-Patter)

In 2059, the Flood infected Bowie Base One's water supply. (DW: The Waters of Mars)

Effect on species
A Thermortian Sand Worm's organs would collapse to sludge if it consumed water. (IDW: The Forgotten)

Skullions didn't drink water as it "burned" them, prefering citrus drinks such as orange and lemon juice. (SJA: The Man Who Never Was)

Seed Pods were resistant to acids, but vulnerable to water. (DW: The Seeds of Death)

A small amount of water was enough to kill a Pyrovile. (DW: The Fires of Pompeii)