Bona Tile Editor
Bona Tile Editor is a Unity Editor extension, making it possible to create and edit NES/SNES-like maps easier, built into the unity inspector and sceneview. The extension also enables automatic collider generation for the maps painted.
There are problably more complete RPG maker extensions if that is what you are looking for. I was looking for a simple solution for just creating the maps which is the problem addressed with this extension.
This extension adds a new resource for setting up tile sets and a new component to used in the scene to create the actual maps, based on a tileset. Tile sets are a collection of layers, each layers consisting on tiles. A seperate texture/image can be used for each of these layers, allowing more detailed, layered, map segments. Tiles have properties regarding if a character can walk on them. This information can then be used for automatic collider generation.