How to close active window with custom keyboard shortcut, only for selected applications

I would like to set up several applications like document viewers and image viewers in Unity to close with one key pressed, preferably when q key is pressed. Most of the applications I use do not have a custom keyboard settings that flexible.

Is there a way to make q quit only selected applications and only if they are in active window? It can not quit any/all applications, because in some I actually want q to work as a letter.