Best can be very subjective.
Hard to pick out a "best ever" but these couple I like.
On a personal level.
#1 What is the relationship of the subject to the photographer.
#2 What was happening at the time.
First evening in Paris. (2008) by
dicktay2000, on Flickr
1/40 (I can hand hold at that speed, with image stabilisaton with out any problems for that lens)
f4 (Wide open)
ISO 1600 = Very low light (after dark)
F=24 mm (on a full frame camera) Not a lot of working room.
Exposure Bias -2/3 EV (to control the highlights)
Exposure Program - Shutter speed priority (That's waht I normally use for vacation snapshots)
Why - it was our (my wife and myself) first evening in Paris on one of our vacations.
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On a more cerebal level where it is mostly content, composition and exposure.
#2
Winter waves by
dicktay2000, on Flickr
1/2000 (I wanted to freeze the droplets
and I was also hand holding a 400mm lens in windy conditions on a 1.6 crop camera( probably could have been a lot lower)
f/5.6 (wide open, subject was a fair way away so DOF wasn't a problem and that lens is ok wide open)
F=260 mm (to frame the subject)
ISO Speed 400 (shot about 1/2 hour after sunrise (I think) in winter
Exposure Program Aperture-priority AE
The main thing with this one is the light.
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Re Settings (and this is for available light shooting).
#1 Shutter speed
What shutter speed do need so that unwanted subject or camera movemt is not a problem?
#2 Aperture
How much depth of field do I want?
#3 ISO
Considering the lighting what is the lowest ISO (Less noise) I can shoot at?
You may not always have the luxury of choising optimum settings so sometimes you just have to take what you can get.