AudioServicesPlaySystemSound(1108);
Based on: Are there any other iOS system sounds available other than 'tock'? and http://iphonedevwiki.net/index.php/AudioServices
For 2016 ....
if #available(iOS 9.0, *) {
AudioServicesPlaySystemSoundWithCompletion(SystemSoundID(1108), nil)
} else {
AudioServicesPlaySystemSound(1108)
}