My proposal defense was at this time a couple of years ago. I had just been visiting my family, and so bought small boxes of local-specialty chocolate at an after-Christmas sale: definitely not lavish, maybe $10-15 each. After the defense (which I passed conditionally), I gave them out to my committee members, who were visibly uncomfortable accepting them. One or two of them even said something about how they weren't sure they should accept them.
On the Chronicle boards, it seems like it's standard to give thank you gifts to one's committee, so I didn't know why they were uncomfortable accepting the gifts.
This time, to thank them and everyone else who helped me during graduate school, I am writing just plain thank you notes written on some cream Crane's cards. It seems like an awfully weak gesture, but for whatever reason they had been uncomfortable with gifts before, and I don't want to make the same mistake.
Did you give thank you gifts to your committee?