Zooropa gets my vote. TUF is the best track IMHO, but the eerie intro to Zooropa, the way Bono transformed slogans into awesome lyrics, and its unique sound represents the best of Zooropa.
All 4 songs do a wonderful job, if you ask me.
All 4 choices, I feel, does a great job in representing their respective albums more or less. But I have to agree with cesar and say that Zooropa makes the best representing of it's album: the ambient sound college and rolling bass as the intro, Edge's eerie open guitar notes which sounds so cool, Bono's manipulated voice and lyrical slogans and Larry / Adam's fluid rhythm section pulsing the song forward, especially the 2nd section. Musically and lyrically, this song sums up the entirety what 90s U2 were about, if not then what Zooropa was about.