Help: Giveaways

I'm thinking of what am I (we're) going to give to my(our) classmates as sort of giveaway or souvenir for our mini-seminar.

I have some options in mind:

1. Test Tube with a play money inside. Since our topic is about cooperative, our giveaway should be a bit related to our topic and cooperative is about money thing, so it looks like a good idea.

2. Vial with a thank you note or still a small play money inside. Just like what i've said about the test tube...

3. Envelope with notepad and pen. I can personalize the notepad and print the seminar title on the front page and on the pen... or whatever

My other options are not really related to our topic. It's like a party giveaway for kids or for non formal occasion. If a reader like you got an idea, please help me :)