I was delaying brewday on a beer for a reason which escaped me at the time... I had all my ingredients, etc. so I figured what the heck let's brew.
When I went to cool my wort, I remembered why I was waiting. I just ordered my immersion chiller and it hadn't been delivered yet. So I had an entire 5 gal brew that I had to cool in a cold-water bath. I had to change the water several times and after about 1.5 hours of this, decided just to put a lid on it and go to sleep. I racked and pitched in the morning when it finally cooled.
Turns out, it was still a pretty darned good brew.