Shake visual effect on iPhone (NOT shaking the device)

I think this is a more efficient solution:

Swift:

let anim = CAKeyframeAnimation( keyPath:"transform" )
anim.values = [
    NSValue( CATransform3D:CATransform3DMakeTranslation(-5, 0, 0 ) ),
    NSValue( CATransform3D:CATransform3DMakeTranslation( 5, 0, 0 ) )
]
anim.autoreverses = true
anim.repeatCount = 2
anim.duration = 7/100

viewToShake.layer.addAnimation( anim, forKey:nil )

Obj-C:

CAKeyframeAnimation * anim = [ CAKeyframeAnimation animationWithKeyPath:@"transform" ] ;
anim.values = @[ 
    [ NSValue valueWithCATransform3D:CATransform3DMakeTranslation(-5.0f, 0.0f, 0.0f) ], 
    [ NSValue valueWithCATransform3D:CATransform3DMakeTranslation( 5.0f, 0.0f, 0.0f) ] 
] ;
anim.autoreverses = YES ;
anim.repeatCount = 2.0f ;
anim.duration = 0.07f ;

[ viewToShake.layer addAnimation:anim forKey:nil ] ;

Only one animation object is created and it's all performed at the CoreAnimation level.

Using iOS 4+ block based UIKit animations (and loosely based on on jayccrown's answer):

- (void)shakeView:(UIView *)viewToShake
{
    CGFloat t = 2.0;
    CGAffineTransform translateRight  = CGAffineTransformTranslate(CGAffineTransformIdentity, t, 0.0);
    CGAffineTransform translateLeft = CGAffineTransformTranslate(CGAffineTransformIdentity, -t, 0.0);

    viewToShake.transform = translateLeft;

    [UIView animateWithDuration:0.07 delay:0.0 options:UIViewAnimationOptionAutoreverse|UIViewAnimationOptionRepeat animations:^{
        [UIView setAnimationRepeatCount:2.0];
        viewToShake.transform = translateRight;
    } completion:^(BOOL finished) {
        if (finished) {
            [UIView animateWithDuration:0.05 delay:0.0 options:UIViewAnimationOptionBeginFromCurrentState animations:^{
                viewToShake.transform = CGAffineTransformIdentity;
            } completion:NULL];
        }
    }];
}