Portal 2's latest DLC doesn't just include the chance to create your own maps, it includes the chance to run around them hearing the delightful JK Simmons - aka Cave Johnson - command, dictate and berate you senselessly with almost half an hour's worth of new content recorded just for the level creator.
If you think sitting and just listening to this for 25 minutes is boring, boy, you're about to miss out.
WARNING: There's technically some spoilers in here.
[Portal 2] All New Cave Johnson Lines (Perpetual Testing Initiative - DLC2) [YouTube, via TDW]