Black Market - Discarded items.
Even though accidental discards arent as much of a problem as they were in the early stages of 1.0, with the addition of a check box confirmation and putting the discard option away from the commonly used repair option, I think it would be cool if discarded items didn't simply vanish from all exsistence.
Instead, they should somehow find their way into the hands of a black market merchant. This special merchant would deal in nothing but items you could have swore you threw away, and sells them at 5 times their vendor price, or really high if it were an un-vendorable item.
Pretty much, this merchant would act as a temporary storage for things you discard and have to pay out the @$$ to get back.