Tiler is a flexible map editor that lets you easily design large 2D tile maps for your game. Built directly into the Unity editor, it provides a custom workspace and integrates directly into various other Unity systems such as navigation.
Check out the feature video here
Features:
-Efficient editing tools including fill and copy
-Generate highly optimized colliders
-Easily bake a navigation mesh
-Tile filters to organize large tilesets
-Easily undo or redo texture changes
-Custom built workspace
-Ideal on all platforms
-Supports both Unity 3.5 and 4.x