I am going to comment on this post all the ideas I get so use them or not I will literally cry either way.

An item that makes Barrels always drop coins when destroyed. Call it like *blank* Greed or something.

I would like to see the Shadow Moses/ Glitch forms of each Character maybe in the labs.

Ya brother requires that Tyson Shop to be actually selling things or him talk to you.

In the Swamp there should be a secret boss. Maybe a big ol' shrimp or something cool like that. Spawning it could require interacting with a ruins-like structure that appears on the map or really any kind of Area interaction could work.

A debug menu to spawn items but I know thats later because items aren't actually their own things yet.