Noob question, sorry.
I’ve imported a lot of junk to my project, stuff I just wanted to try out but ended up not using. When I export the game, does all this get included too? I assumed it would only include what was in my scene, but I see some references to things that definitely should not be there.
http://docs.unity3d.com/Documentation/Manual/ReducingFilesize.html
Unity strips out unused assets
The amount of assets in your project folder does not influence the size of your built player. Unity is very smart about detecting which assets are used in your game and which are not. Unity follows all references to assets before building a game and generates a list of assets that need to be included in the game. Thus you can safely keep unused assets in your project folder.
If an asset is not in the scene and you have nothing which references it, it will not be included in the build. For basic questions like this, it usually best to look through the documentation before asking a question on answers. Unity has wonderful user friendly documentation.