‘The Cold Equations’ by Tom Goodwin
This is one of those stories where the hero has to shoot a puppy to prove what a noble but tough consequentialist he is. Obviously in order to do so the author must massively stack the deck; in this instance, Goodwin makes the logistics ridiculously tight and the security ridiculously slack.
‘The Cold Equations’ is one of the most famous SF stories ever written but knowing the punchline meant there was no reason to actually read it and I spent the whole story waiting for it to be over. I did like this bit though:
Yet, to protect such as her from the results of their own ignorance of the frontier, there had been a sign over the door that led to the section of the Stardust that housed EDS’s; a sign that was plain for all to see and heed:
Wow, that is a strongly worded sign! Who wouldn’t expect to be pushed out of an airlock after disobeying it?