Methylene blue is the most surprising of them all. It’s often used as a cationic stain (so it reacts with negatively charged stuff) for bacterial identification and “making cells more visible”.

I barely understand how it works but also heard that is used intravenously for some anoxia issues by some smart doctors but with someone not suffering anoxia, that seems like a thing that you don’t want in your body.

Edit: and as an aquarium dye to battle fungal infections.