If I had a Togekiss with Serene Grace, a King's Rock, and Extrasensory (which I do- why would I ask this if I didn't?), what are the chances of Extrasensory making the opponent flinch? Pretty good I assume, or am I wrong?
King's Rock does not effect Extrasensory. So no. As such, only a 20% chance at flinching. Use Air Slash, it gets a 64% chance at flinching with King's Rock and Serene Grace.
P + (1 - p) * 0.1 is the formula for King's Rock.
A pokemon with serene grace and a king's rock using Air slash would have a 64% chance.
Only 20% chance so not really