A faked donation to charity. Surely I win?
Had the "what does everyone want for Christmas convo with DBIL November time. He said just to get him and DSIL charity gifts, I said please do the same for me. A few weeks later DBIL rang again because he'd forgotten what I'd said (easy to remember no? it was the same thing they suggested we give them).
I quite enjoyed browsing charity gifts to find one each for DBIL and DSIL that was relevant for each of them.
We didn't see them at Christmas and the gifts sat on the side until Feb/March when we saw them next (NB this is standard practice with this branch of the family). DH met them while I was at work one weekend. I was pleased to see the back of the pile of gifts and on return from work enquired what they had given me (expecting a goat from Oxfam or similar).
DH said DBIL and DSIL "had a problem with the ordering" and it hadn't arrived. This was several weeks after Christmas. A couple of days later I got a slip through the post of the exact thing I had got for DSIL, which had relevance for her but none for me (it was maternity kit for expectant mother in poverty, she was expecting long awaited 2nd child, we had no children and had never mentioned wanting any, so it would be a bizarre gift for me). So she took the gift token out the card I gave her and had stuck it in the post back to me rather than actually give money to charity, the very gift she and DBIL had themselves suggested.
This was about 10 years ago, I've never had it out with them, but I haven't ruled it out.