I got a question for you: "I Still Have n't Found What I'm Looking For" is a song by Irish rock band U2. It is the second track from their 1987 album The Joshua Tree and was released as the album's second single in May 1987. The song was a hit, becoming the band's second consecutive number-one single on the US Billboard Hot 100 while peaking at number six on the UK Singles Chart.

Answer this question: who sings but i still haven't found what i'm looking for?
Let's think first:
This is the relevant information: "I Still Have n't Found What I'm Looking For" is a song by Irish rock band U2.
Therefore, the answer is Irish rock band U2.