1 - Bingo: Get a list of some uncommon caps/boards/other that people will be bringing, and make a bingo sheet out of them.
2 - Crowdsourced sculpting: pass around a sculpt and let everyone add 1 thing, such as a line, adding a piece...
3 - There was a mention of a soldering contest, which is cool, but would take a bit more planning that I'm not knowledgeable enough to source.
I'm pretty sure I had a couple of other ideas, maybe they'll come back to me when I'm less tired. I like the suggested ideas above as well.