Is the word 'you' needed when you call someone using an adjective?

[99bottles]

For example, is it needed in the sentence below? (Let's say that someone asks something you have already answered and you say this.)

I already told you, (you) silly boy.

 

[Rover_KE]

It's optional.

 

[Tarheel]

In either case, it's a perfect opportunity to use an exclamation mark, thus:

I already told you, silly boy!

Or:

I already told you, you silly boy!

:-D