StarCraft II: Heart of the Swarm/New Terran units

Hellbat
Hellions can transform into tougher, slower and stronger walkers with shorter range but the splash damage is wider.

Widow mine
Widow mines burrow and launch missiles at enemy units and causes major damage in a radius.

Reaper
It cannot be upgraded with its speed boost upgrade but can self heal itself outside of battle.

Hellion
Can now transform into the Hellbat.

Siege tank
Does not need upgrade to switch to siege mode and tank mode.

Thor
Can now switch between two modes, Explosive payload and the Punisher cannons.

Medivacs
Can now use a speed boost to get to places faster.

Battlecruisers
Yamato cannons take up 100 energy instead of 125.