Giving out rare items to users with good item combining ideas!
For example, 1000 sprinkles can be combined to create a large sprinkles gem.
Or 1000 limes can be combined to create a lime statue.
You get the point. I want things that users must collect that can be combined to create stuff.
Also to make things fun, I can make combining items produce a random item, or produce an item that only has an X percent chance of being created.