Besides the Ki power Mongoose’s Artful Dodge, is there an other way to gain an additional Response action? I looked through the talent trees and did not see anything there.
Dark Defense (Mysticism Talent) MC3 core book p. 98.
As a Standard Action, during a combat where there is at least one Heretic or creature of the Dark Soul on the opposing side, he may attempt an Average D1 Mysticism test. If this test is passed, he gains a free Response Action against an attack from a Heretic or creature of the Dark Soul, due to his defensive tactics. For every Momentum spent, he gains an additional free Response Action. These free Response Actions may be used at any point before the end of the combat.
And then there are Mutant abilities that allow additional Response Actions, too.