Splash Potion

Splash Potions are a variant of Potion which may be thrown as a weapon. The player can turn any brewable potion into a Splash Potion by mixing one with Gunpowder. Their flask has a different shape than the original, resembling more of a Retort-type flask. Not only can the player throw these potions, but they can also be released from Dispensers. They can effect both passive and hostile mobs. This gives purpose to negative potions as weapons against enemies, although some are immune to certain effects. Positive potions can be used to help, such as on wolves or livestock to recover their health.

Brewing
For ingredients that go into Potions, Splash Potions, and known Potion recipes see Brewing. According to Jeb there are 161 possible potion combinations in Beta 1.9 Pre-release 3, and there may be 2,653 potions in the full release.

Mob Immunity
Certain Mobs are immune to damaging splash potions such as Poison and Instant Harm. In 1.9.5 These potions heal the targets.

Note: Immunities needing further confirmation are in italics.

Note 2: In Pre 1.9.5 Heal Potions Damage and Health Regnerations Poisons Zombies, Skeletons and Zombie Pigmen

Trivia

 * The effects of Splash potions travel roughly five blocks from the place it lands, the effects weakening the further away an entity is from the center.
 * Splash Effect Potions will affect the player if they are within it's radius. This can be dangerous with harmful potions, but useful with positive potions; a group of players clustered together can all benefit from the effects of a single potion, depending of their distance from the center.
 * Splash potions can do minor explosive pushing damage, although this does not seem to harm Creepers and Skeletons in Creative Mode.
 * Jeb has said that while water splash potions should logically harm Endermen, its coding would be too difficult to implement.
 * The time a Splash Effect potion lasts is decreased slightly from the original version.

Bugs

 * In Creative Mode, throwing a Splash Potion in Beta 1.9 Pre-Release 4 and then opening a chest or any other object causes the Splash Potion to reappear in the same slot it was before.
 * According to Jeb, Skeletons, Zombie Pigmen, and Zombies are supposed to be damaged by Splash Potions of healing."Yes, that's a bug, sorry... Totally failed at writing an if-statement. Undead are supposed to be harmed by healing, as expected"