I was thinking it might be interesting to have a "gift card" system. Where users can buy an item or set aside a sum of money to spend in the marketplace. It could also be used by admin as a reward, for example for winning competitions.
What I could consider for that is to allow a user to buy on item for another user.
But that would be for digital products or services as for physical products you already can if you just set that other user posting address.
From my thought the idea would be "the gift" not that you practically can send something to someone else but that someone can gift you a purchase of certain value.
One way I could see it work would be if it was monetary value with possible restriction to category or an item.