Channel specific currency for Interactive events
A customizable currency unique to each channel.
Example: Let's say I have an interactive game that has its own economy. I want to be able to freely control balancing that economy around a currency I control. Being able to grant and remove funds based on game events, subscriber status, etc without worrying about Sparks influencing my economy.
An argument can be made that developer could simply implement their currency on the game side; personally I don't think that doesn't lend itself to a good user experience. Users would have to use a chatbot to query their inventory state, making the experience substantially less accessible and intuitive.
A lot of this is also predicated on new Interactive API features allowing for more user-specific interaction.
blipbot/streamjar does this
Jon Terp commented
A more generic expansion on this concept would be a per-user inventory that can receive objects (items, boosters, currency) granted by a channel running an interactive game.