I saw this in today's Straits Times, Home section. The words in italics are my suggested responses :)

1. I am buying it for my father.
Tell him to come himself.

2. I forgot to bring my IC.
Come back when you have it.

3. I'm 17, and my birthday is in two days' times
Since you've waited nearly 18 years, another 2 days isn't too much.

4. I know the boss here, it's cool.
The boss isn't bigger than the law.

5. It's only 2 per cent alcohol, it doesn't count.
Ok, if 2 per cent is so insignificant, buy some grape juice. No difference right?

6. My friend bought some yesterday and you didn't check him leh.
Well today I'm checking you.

7. Yesterday, the newspaper reported that the age limit is now 16.
All right, show me.

8. I'm not drinking, it's for my science project.
What's your project about?

9. What if I buy in bulk?
Even worse.

10. How about I buy you one too?
I don't drink. Don't want to destroy my liver.