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 affect 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. Splash potions can be thrown to the ground to be consumed making it faster than drinking a regular potion.

History
Splash Potions were introduced in Beta 1.9 Pre-release 4.

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 later.

Mob Effects
Splash Potions can have varying effects depending on what they are used on versus what they actually are.

Note: Effects needing further confirmation are in italics.

Splash Potions
Here is a full list of the names, effects, and damage values of splash potions that are currently obtainable through Brewing. Note, that the base duration of splash potion is always 3/4 the duration of corresponding drinkable potion.

Unbrewable splash potions
This class of splash potions exist in the game code and are functional, but cannot be brewed. This seems to exist primarily as potions that have both an extended mode and empowered mode, but the brewing process normally only allows for one of the two to take precedence. Thus, these potions result from custom data values that place both effects on the potion.

Potion Jump
By simultaneously throwing a Potion with the Instant Harm effect and jumping, the player will be able to jump 2 blocks high instead of the usual 1. Try to face backwards to the area you wish to land on when doing this. It is recommended that you use a Potion of Regeneration in addition to prevent death.
 * Video Example

This happens because when a mob or player receives damage, they get a knockback. This knockback creates some vertical momentum. This is the momentum that is used to boost a jump.

Trivia

 * The effects of Splash potions travel roughly five blocks from the place it lands, the duration shortening the further away an entity is from the center. For potions that have no time parameter (i.e. Potion of Healing, Harming) the effect is weakened instead.
 * Splash Effect Potions will affect the player if they are within its 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 on 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 and Blazes, its coding would be too difficult to implement.
 * Splash effects are slightly less than expected. Standing against a block at eye-level and hitting it with a potion gives you the longest duration, as opposed to straight down.
 * Splash Potions of Poison and Harming will affect other players even on Non-PVP SMP servers.
 * Splash potions of harming are very effective in PvP as they bypass armor.