There was once I went on a Bangkok trip and the fastest lens I brought was the Olympus 17mm f/1.8 lens. The video footage I shot at night with the GH3 was unusable because of noise.
I told myself that I must bring the Voigtlander 17.5mm f/0.95 for the next trip.
In my most recent trip to Cambodia, I brought the 20mm f/1.7 lens instead. I wanted to pack lightly. BIG MISTAKE AGAIN! Turned out that the video footage at night is unusable again.
So the next time when I go on vacation, I will bring the 17.5mm lens regardless of weight, even if it's going to be the only lens I bring.
If you have that lens, bring it even if you have to leave it in the hotel. When you need it, it's a life saver.