Precious metals bullion/coins
Patents
Positions in sports outcomes (either with bookmakers odds or betting pools)
Positions in real life outcomes (predictions markets and British oddsmaker offering real life outcomes)
Non perishble objects and collectables of any kind that can be re-sold including art
Hotel reservations where you can change name or add name (almost all hotel allow for it, maybe some minor fee, but it's irrelevant compared to the potential gain you can make by selling your reservation to somebody else who needs it)
Airline reservations where you can change name
If you are a freight forwarder/NVOCC you can buy container space slots on ships and then sell it to other freight forwarders/NVOCCs.
Ad space (physical, newspaper, magazine and online) where you book the space and then have in your network people who might be interested in that very space so you can run their ads and they can re-imburse you
... and I am sure there are many others