You are speedling a base when he surrounds his sunken with drones, your zerglings can't reach the sunken with the drones in the way, so they swarm is endlessly. Do you:
a) start clicking on drones
b) queue attack as many drones as possible
c) micro a zergling to each drone as fast as possible
d) hold position

Just keep harassing and threatening to attack. Each time he pulls his drones off his mineral line, hes losing minerals, thus putting you in the lead. You can then take the time to expo, tech up, or mass and go for the win.

Eh, it was a 2v2 game where they destroyed Cent's econ with reapers and speedlings. This was a retaliation attack and it had to do as much damage as fast as possible, so that's not an answer. I wanted the drones dead anyways, but the sunken had to go first.

But in all other situations, I suppose that could be a nice response.

You pull out. Losing lings when you're already forcing drones off the line is bad. He has to move those drones sometime so just go elsewhere to harass in the meantime.

That's what I was thinking. Losing the lings is like losing your red-hot poker that you're shoving in his face. It really doesn't help if they get turned into little splats of blood streaming across the creep, trust me. Or at least, not all at once. So long as you still have some left, there's a danger to your enemy and he knows it, too.