I don't have much to go on as I don't have much of a collection but my worst buy so far must be a pack of rubber pants I got from Mothercare. We were short on wraps so I thought they might be good as a back up. How wrong was I?! I used 1 pair, they went on for about half an hour and he ended up with a horrible red mark on his leg for a week
I now have a whole pack sitting here which I'll never use again. Cheap, admittedly, but total waste of money.
On the off chance that anyone actually does like these things I can post the pack to you. They are small - up to 6.5kg (Doubt very much anyone likes them though)