Shuck Shot should be easy to identify, as usually, Kernel Corn will yell before it is fired. Not only this, a large yellow particle appears on Kernel Corn's cobs, which also signal that it is going to be fired.
If you cannot do anything to an incoming Shuck Shot, use any ability that gives you mobility, as this will allow you to dodge the Shuck Shot if you time it correctly.
As Kernel Corn, vanquish 25 Zombies with Shuck Shot.
Gallery
Kernel Corn firing his Shuck Shot at a Moto-X Star
Shuck Shot being used in the trailer
Shuck Shot's current icon
Trivia
It firing explosive cobs and exploding into popcorn may be a reference to the Cob Cannon as it also fires explosive cobs that release popcorn when exploded. This is further emphasized by the great amount of damage it does.
Sometimes the corn will not fire but still enter cooldown after the ability is used. This is a bug.