Throwies! Otherwise, have a scan through the various LED projects to see what grabs your fancy.
I'm still waiting for someone to make a Knex gun that shoots throwies. That would be AWESOME!!!!
Why wait for somebody else to do it, when you could be first?
As awesome as it might be, it's not awesome enough for me to go out and buy a bunch of K'nex that I would never use again. RavingWife would be less than amused.
You should totally make this. It's useful and u'll learn something.
For putting LEDs into things, I prefer this one L