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I think USB drives would be very attractive.

My dad went to a chemistry conference not too long ago and brought home some interesting freebies like a swiss army knife and a laser pointer :p
 
In my personal opinion, 8 MB flash drives are essentially useless, you can cary your papers, but that is about it. I would go with bigger flash drives, 64 mb+ (if you can afford them) or a laser pointer, they're cool. However, a bottle opener is clever and I'm sure would be appreciated;)
 
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