HelveticaNeue-Bold is the identifier. Here is a snippet of code you can use to list all the available fonts:
NSArray *familyNames = [[NSArray alloc]initWithArray:[UIFont familyNames]];
for (NSString *familyName in familyNames) {
NSLog(@"%@", familyName);
NSArray *fontNames = [UIFont fontNamesForFamilyName:familyName];
for (NSString *fontName in fontNames) {
NSLog(@"\t%@", fontName);
}
}
*Edit: Swift 3.0
for familyName in UIFont.familyNames {
for fontName in UIFont.fontNames(forFamilyName: familyName) {
print("\(familyName) \(fontName)")
}
}