Wikis where HotCat is available as a gadget, but is broken (as of October 5, 2015):
ar.wikinews.org
arz.wikipedia.org
av.wikipedia.org
az.wikiquote.org
az.wikisource.org
bd.wikimedia.org
bjn.wikipedia.org
bug.wikipedia.org
bxr.wikipedia.org
de.wikinews.org
de.wikiquote.org
fa.wikinews.org
fa.wikiquote.org
fa.wikisource.org
fa.wikivoyage.org
fa.wiktionary.org
fi.wiktionary.org
fr.wikinews.org
gan.wikipedia.org
hr.wikiquote.org
id.wiktionary.org
kbd.wikipedia.org
ksh.wikipedia.org
mk.wikisource.org
mrj.wikipedia.org
mzn.wikipedia.org
nv.wikipedia.org
sl.wikisource.org
zh.wikibooks.org

Also HotCat is half broken on az.wikipedia.org. Part of the UI loads, and part of it doesn't load.