Who am I? A mutation of the Zergling, the beetle-like Baneling is a neon-green suicide bomber that explodes on contact with an enemy. Best used en masse to level opposition structures.
Most likely to: Squirt green sticky stuff in your face.
Who am I? An advanced unit used to build tunnels by creating entry and exit points anywhere across a map.
Most likely to: Only be used by clever players.
Who am I? Great to look at, this base defence expert is actually a bit futile as a protector and is killed off quickly in a fire fight. She's good at healing damaged units and creating battlefield diversions like Toxic Creep which makes a small area of 'creep' (the grey mucus stuff that the Zerg grow their base on) damaging to any unit standing on it.
Most likely to: Get killed before you get any use out of her.
Who am I? These evil bastards are the most lethal melee characters StarCraft II can offer. Send a large unit of these in to attack an unprepared base and they'll ransack the place and run away unscathed. Their secret is their ability to regenerate from damage very quickly.
Most likely to: Really f*** you up.