Altered Zerg Unit: Ultralisk
The Ultralisk remains as powerfully huge as ever, but he's now learnt how to muscle his way past pesky Marines. Press C and aim your Ultras forward and they'll hurtle underground like a chitinous torpedo. It renders ramp defence pointless, allowing large quantities of Starcraft 2's biggest monsters access to the heart of your base. But, realistically, Ultras are a late game unit choice, meaning the HotS change is one to reduce Zerg annoyance - Ultras would happily clump around single units they should be able to trample over - rather than add a new unit function.