I think my roll of butcher paper is maybe my most valued gaming tool that isn’t on the obvious dice/pencils/paper list.
I can’t think of the last time I didn’t roll some out for a game I ran. Maybe The One Ring, which doesn’t really lend itself well to relationship maps.
It’s super handy during design when I need to see a lot of interrelated ideas at once. This afternoon I hashed out a first draft of my glorious combat (yes it’s ironically named) system for The Secret Project.