Shin-ei 6-TR Fuzz-Wah (left of Big Muff), from "Stompland"
Combo fuzz/wah pedal. Used on the solo of "Untitled".
Featured in a video of Billy's huge collection of guitar pedals called Stompland (black wah pedal left of the Big Muff Pi).
Tweeted by Billy on 2011/09/05: "Bat strat>Companion wah>Beano Boost>vintage Orange head=happy Labor Day everybody"