BioShock Little Sister

Little Sisters are genetically altered little girls who harvest a chemical called ADAM from corpses in the Xbox 360 and PC video game Bioshock. Though the player fights Little Sisters, the ADAM they carry is needed to advance in the game. Before players can take it from a Little Sister, however, they must first defeat the guardian of the Little Sister, a fearsome Frankenstein monster in an antique diving suit called a Big Daddy.

In BioShock, after players defeat a Big Daddy, they are given the choice of saving his Little Sister by removing the parasite inside her or harvesting her by killing the girl and taking all of her ADAM. Since harvesting yields twice the ADAM as saving, it would seem like the best choice. However, after 3 Little Sisters are saved, Dr. Tenenbaum gives the player a gift of 200 ADAM, a tonic, and some ammunition for his kindness toward the disenfranchised children. A comparison shows that 3 harvested sisters gives 480 (160 times 3) and nothing else, while saving 3 brings in 440 ADAM (80 times 3, plus 200 from Tenenbaum), a tonic or plasmid, and ammunition. The choice is ultimately up to the player, but if he or she chooses to harvest even one Little Sister, the "good" ending will not play when the game is completed.