Good ideas for freebies

I'm on work experience at the moment and I've been asked to think of ideas for freebies that would be good to give to 15-18 year olds. I've come up with a few ideas so far. To help me a bit, which do you think is the best idea.

1. Stess ball

2. Key ring laser pointer

3. Playing Cards

4. Memory Stick

If you have any other ideas please post them.

Thanks in advance.