Infantry units train 20% faster. Barracks build 50% faster. 

Data in the Galaxy Editor points to Swann having access to Diamondbacks at some point in development 

Data exists in the Galaxy Map Editor for a Devouring Maw ability for Zagara in Co-op Missions, similar to her Heroes of the Storm appearance 

A mobile Nerazim Mothership would be at the center of her base rather that a static base 

In early screenshots of Alarak in Co-op Missions, he was shown alongside Tal'darim skinned Zealots. These zealots are absent in the release version 

Able to build an elite variant of the Reaper

Able to build an elite variant of the Cyclone

Able to build an elite variant of the Medivac

Nova was able to build an elite variant of the Bunker in early versions

Started out with an Orbital Command Center

There is also data indicating that Nova would have been able to summon the Odin to the field at some point in development 

Used to create Drones and Mutalisks, was later replaced with the infested SCV

Replaced by infested SCVs, they functioned similar to the standard Zerg Drone but these could morph into infested structures as well

A cheap infested air unit that was later replaced by the Infested Liberator

Early Stukov used this building for all upgrades, was replaced with the Infested Engineering Bay

Stukov's Mutalisk, unknown abilites

Early way for Stukov to increase his supply, was later replaced by Overlords

Stukov was suppose to be a hero unit that spawns after 240 seconds from the Infested Command Center, was later replaced by the Aleksander 

The Infested Barracks also appeared to operate similar to the Infested Colonist Compound at some point in development, spawning Marines for free in waves and having its own tiers of infestation upgrades 

A anti air unit that was later replaced with the Infested Liberator

A heroic unit similar to the Apocalisk

Data and images in the Galaxy Map Editor show Fenix was intended to have Instigators at some point in development, likely scrapped instead for the adept 

Cut Purifier Immortal meant to be more resistant to damage, was later reused by the hero unit Taldarin

Cut Purifier Carrier said to only use Interceptor Bombers, was later replaced by the Hero unit Clolarion

A Primal Zergling mutation

A Primal Mutalisk mutation

A Primal Mutalisk mutation

At some point in development Han and Horner had access to Warhounds 

Mira Hans long ranger bomber 

Han Marines created Valkyries but were not expended when created since the Valkyrie had an AI pilot

Mira's Marines, they use the Trooper model

Mira Hans starfighter built by Han Marines

Expends 1 Han Marine to make 1 Griffon

Originally built by the player and not given on start, could originally lift off

Would have been used for unlocking unit upgrades instead of the Tech Lab, Armory, or Engineering Bay

A calldown ability, would calldown an Ordnance Tower from space to fire upon enemy forces and act as a defensive structure

Han and Horner's defensive structure can still be seen in the editor as the HH Gun Tower

In early builds, Blaze was replaced with a Hellbat/Hellion based around the druid class in Warcraft

Early cut idea for a Siege Tank Outlaw

Many believe it would have been Sgt. Hammer

Early cut idea for a Widow Mine Outlaw

Tooltips on the Mecha Spire referred to Stetmann being able to spawn Mecha Mutalisks, and Mecha Mutalisks show up in his commander trailer 

Data in the Galaxy Map Editor exists for a Mecha Roach Warren 

Originally a permanent unit and not a timed life unit from the Mech Infestor