Making GLaDOS speak

It's actually very easy to make GLaDOS talk, but which method to use may not be immediately obvious. You can play one of her lines using an ambient_generic, but this has an unfortunate downside. ambient_generic entities continue to play even when the game is paused (hence the "ambient" part of the entity name).

In Valve's maps, a logic_choreographed_scene is used instead. Here's how to make GLaDOS speak in your own maps with a logic_choreographed_scene entity:

1. Create a small room outside of your regular play area. Cover the walls with the "nodraw" texture.
2. Inside the room, create a generic_ai entity. Set the entity's model to metal_box.mdl or something similar. The model doesn't really matter, but Valve uses metal_box in their maps.
3. Set the generic_ai entity's Name property to Aperture_AI (the name cannot be anything other than Aperture_AI, otherwise the scenes will not function)
4. Create a logic_choreographed_scene in your play area and set the Scene property to whatever scene you want to play.
5. Now, just trigger the logic_choreographed_scene entity and listen to GLaDOS speak!