I'll call this my LLL (Least Loved List):
1. Unknown Caller. This is the only song I would comfortably attach the descriptor of "worst" to. More than that, it's lyrically an embarrassment and it hurts me to listen to it. Can't imagine how that slipped through QC. Ugh.
2. Breathe. "Cockatoo"? Come on. Music isn't bad, but the lyrics are tired U2 rehashes not dressed up very well and poor rap-style verses.
3. Magnificent. Again, music isn't bad. Again, lyrics are so unoriginal for the band, and the majority of it has been done infinitely better one earlier albums, as recently as HTDAAB. I'll limit NLOTH to these 3 so I can spread the love some more.
4. Miami. As others have already mentioned, this song didn't succeed at all for me, musically or lyrically. It's uninspiring and doesn't invite the listener into it. It's weird not to be emotionally involved in a U2 song!
5. This is probably going to be sacrilegious, but here we go: Mofo. I know, I know. It's "Bono's most personal song" and all that. It was a show stopper during PopMart, I guess. But still, try as I might, I've only been able to gain a grudging respect and appreciation for it. If I hadn't worked so hard, I probably wouldn't be able to listen to it without effort. It's just not a U2 song to me, musically mostly.
Like some people said before, it's not easy to pick out U2 songs for the bottom of a list. If it wasn't for NLOTH and the two Pop tracks above, I don't think I could have supplied such a list at all.