My mother is an expert at re-gifting. For an engagement present, DSis received a bowl she'd spent aaages saving for as a teen, for parents wedding anniversary.
Instead of donating to charity shops, my mother would send us her unwanted stuff, including pants, that had been worn and washed so many times, the elastic was hanging out.
Once DSis got sent a pair of pants for her birthday, sadly the wrong size. When she took them to be exchanged for the correct size, the assistant informed her they'd not stocked those pants for about 5 years. 
A few years back, I bought my mother a silver necklace and bracelet set, very understated and wearable. Guess what I got for my birthday a couple of years later?
The best was one christmas, which I was spending with DSis. Parents had just sold their caravan, and were obviously having a clear out. My present was in a huge cardboard box, no original packaging. Inside, cushioned with newspaper, was an electric frying pan, which had scratches on the bottom, and smelled of grease. A note wafted out, "I thought I'd try it out first, it's marvelous!" DSis (who I was spending Christmas with) said she wasn't sure if I was going to laff or cry. Laff we did, almost wet ourselves.