I'm a huge fan of this format for sci-fi, so it's a hard choice. Probably "Goodnight Mr. James" by Clifford Simak. Honorable mentions to: "Microcosmic God" a

I'm a huge fan of this format for sci-fi, so it's a hard choice. Probably "Goodnight Mr. James" by Clifford Simak. Honorable mentions to: "Microcosmic God" and "If all men were brothers would you let one marry your sister?" by Ted Sturgeon "Bordered in Black" and "Neutron Star" by Larry Niven "Blood Music" by Greg Bear "Special Delivery" by George O. Smith "The Gold at the Starbow's End" by Fredrick Pohl