Magic - the smallest difference in the world. . . .

[BryonD]

Any of the above: I will assaulted and murdered by my tribe as an associate of devils.



Sorry, probably not very helpful to the thought experiment. But most likely accurate.

 

[Macbeth]

Assuming a substantial part of the population could cast the spell:

Magic Missile would change the nature of hunters somewhat: no more need to physically overpower your prey. I suppose you'd still need to catch it, but imagine a society that just hunts by ambush: spend your days napping in the brush until some animal comes by that you magic missile.

Even in war, the warriors wouldn't need to be all that physical. I would envision the society tending towards higher CON scores, but less STR. Not by genetic difference, but by how they're rasied: hearty diet, but not much need for excessive strength.

Basically, for me, this brings to mind a hunting group of overweight guys that sit around till something to kill comes nearby. Something more akin to modern hunting then historical hunting.

 

[Tarrasque Wrangler]

To build on what WayneLigon said, I'd say Unseen Servant has the most far-reaching implications for a society. A people that don't need to break their backs all day long could theoretically have much more free time to develop intellectually. Sure, they might be all fat and lazy and lying in hammocks all day, but they might have developed string theory and quantum physics while the rest of the world was grappling with how to build a better thresher.