Machoke's "Knuckle Down" attack says the amount of damage is "not affected by Poke-Powers, Poke-Bodies, or any other effects on the Defending Pokemon". Does that mean it ignores Weakness & Resistance too?
Weakness & Resistance are not considered as effects on the Defending Pokemon, so they are not ignored.
Source: PUI Rules Team (2011-06-09)

Relevant cards

Note: All applicable cards may not be listed below.
HGSS4_40