I can be cruel, but I have my limits. While I don't want to put in spoilers, I can't bear the thoughts of harvesting...
Funny story, I didn't get to play the first BioShock until late last year, almost two years after it was released. Looking forward to for that long, I conditioned myself to run a harvest game first, then I'd run a rescue game on my second play through.
Then I got to that scene with the first Little Sister. I had planned a harvest game for over a year, but that scene... I had to get up for a few minutes and pour myself a good stiff drink before I was able to come back to the game and hit the harvest button. I harvested all of them. Then the game throws it right back in your face, like you rightly deserve, about midway through.
And with the Adoption system in the sequel, and the new Little Sisters' dialog, they make it 10,000 times harder for any sane human being to harvest one. I told myself I'd start another harvest game for my first play through. Again, it took me several minutes to hit the square button.