Outline Image Effect for Unity
Merged outline between multiple sprite/line renderers
Erase option to keep outlines behind specific sprite/line renderers
Per sprite/line renderer color support
Download the files and open the project OR place the "Assets/OutlineEffect" folder in your Assets folder
Add a layer called "Outline"
Add Outline Effect component to camera
Add Renderer objects to "Outline Renderers" in the script OR replace the list from your scripts
I do not own the Half Life sprite and it's used for demonstration purposes only under fair use.