Yesterday I was hearing F for you by Disclosure and I loved the vocals they have.The effect is really appealing to me. The thing is I thought they kind of dubbed the vocal and added some king of reverb in the studio, but when I saw the live performance it was just one guy singing into the microphone. This made me realize they must be singing into some kind of harmonizer with a reverb and a stereo enhancer... maybe. The thing is, I don't know how they achieve that vocal effect... any ideas??

https://www.youtube.com/watch?v=5TUIciKQzxI

The vocal I'm talking about appears at 0:10

This isn't any special trick, this is a standard technique called double tracking. The vocalist, guitarist, or whomever you're recording repeats the same musical phrase twice, and you pan one take hard left and the other hard right. The simple fact that they are not the same recording and our voices can't recreate the exact same sound twice means they contain different enough harmonic information that they provide that really nice spread out sensation. if you listen to the song with headphones it becomes especially clear, because you can make out the slight differences in how he sings the left signal and the right signal.

Plus, since they aren't the same recording, they won't double or phase cancel - completely mono compatible!