Thumbs down on the flash drive. I would think that if you work in a technical field, your co-workers would already have their data storage needs figured out.
Typically, the worst gift to get someone is a gift that has to do with what they are "really into". Why? Because, when someone gets really into something, the result is that they have very specific things that they want/need. They have done all of the research on all of the hundreds of products available, and figured out what the very best is - and then they buy it for themselves. Golfers often complain of this - they hate to get golf-related gifts because they already have exactly what they need for golfing.
I am really into photography, but if someone were to try to get me a photography-related gift, it wouldn't be anything I'd want, because I already have all of my photographic stuff figured out, and if I don't already have something, it's because I don't want it and don't need it. And the moment I discover something new that would be of use to me, I just do the research and then order it myself.
Perhaps you could do a special, one-of-a-kind gift to bring to the exchange. You could have a calendar made, using your photos. You could go thru your photo library and pick out the images that you think would have the greatest appeal for your co-workers; photos that would specifically appeal to those who live and work in your community. Lulu.com makes some really nice, extra-large, premium calendars that still fall within the $25 limit:
Here's a link, if you're interested:
"Your" and "you're" are different words with completely different meanings - please use the correct one.
"They're", "their", and "there" are different words with completely different meanings - please use the correct one.
"Fare" and "fair" are different words with completely different meanings - please use the correct one. The proper expression is "peace of mind", NOT "piece of mind".