Hrmmm.. as a big fan of industrial music, I'd have to go with anything from the AB/Zooropa period - ya know, their more "gothy" period (But then again, that's my subjective take on their "dark" period)
In addition, HMTMKMKM would make a wonderful industrial song if maybe Chris Vrenna did it.
Think the best song to remix still is "Bad" 'cause of it's building repetitive structure.
Wanna hear somebody doing something with it...not a dance version but a dark industrial version would be nice