I've already experimented and build my own small MRE-object (in this case a dynamic changing text showing the current block produced, witness and amount of tx to put on display as a ticker in the hivefest world)

Here is the dev docs. https://developer.altvr.com/get-started/

Simplest I can think of is a button to be found and then pushed to get a badge on your profile. More difficult is an object which can be spawned and passed to someone else and then handed in again. (something like a business card exchange).