From the developer of Alien Blue for reddit.

Game Pauser gives you the power to pause your games and cutscenes at any time.

Un-pausable cutscenes and un-pausable games no longer need to be a source of frustration.

It is free to use, source available and respectfully developed to value your time.

Features

• Pauses un-pausable cutscenes and un-pausable gameplay
  
• Perfect for Mouse & Keyboard gamers
  
• Perfect for Controller / Gamepad gamers
  
• Re-mappable Keys and Gamepad buttons for pausing/resuming
  
• Hand-crafted, minimal and compact interface design
  
• Sleeps in the background and stays out of your way
  
• Incredibly easy to use
  
• Allows using your phone as a back-up if a game doesn't allow pausing via Keyboard or Gamepad
  
• Subtle audible cue to let you know that the game has paused/resumed
  
• Dark UI theme for visual comfort
  
• Ability to include / exclude games and folders that can be paused
  
• Advanced customisation available through well-documented configuration files
  
• Runs without admin / elevated permissions
  
• DRM free and can be run independently (even without Steam)
  
• Source available for personal and educational use
  
• Gives back control over your time

DO NOT USE with Multiplayer Games, as doing so may lead to getting kicked off a server or banned. This product is intended only for Single Player experiences.

ALWAYS test games with a new save file first to ensure the game handles pausing without issues. Alternatively backup your save files beforehand to avoid any risk of save file corruption.