Unity's editor console is indispensible, but retrieving debug logs and warnings
outside the editor is difficult. To make it easier, this console displays
output from the Debug class, as well as any errors and exceptions thrown, in
the game itself. This is especially useful on mobile devices.
Attach this script to a game object. The window can be opened with a configurable hotkey (defaults to backtick). Alternatively, enable shake-to-open in the Inspector to open the console on mobile devices (with an option to prevent accidental shakes by requiring 3 or more fingers on the screen).
Supports Unity 5, 2017.x, 2018.x, and 2019.x. It hasn't been tested on all the platforms that Unity supports but it probably works on most.