I was thinking about my 7th Sea sandbox. "Wouldn't it be fun," thought I, "if the players had an NPC along to talk to, protect, pull out of deathtraps, and generally interact with?" Because I do love GM NPCs. When the ninja assassin Silver defected to the PCs' superteam in the middle of an all-out ninja assault,* she generated many sessions' worth of tension and subplots, along with a longstanding romantic thread for the one player who enjoyed that kind of thing. When the cleric wanted a wizard hireling, I gave him the crazy wizard dude from the Conan movie, thrilling him and annoying the ranger no end. GM NPCs are great.
But not everyone loves them. I'm not even talking about the problems with the GMPC - the dude who outshines everyone else because they're the GM's secret special pet character. I rein 'em in better than that. There are just some players who don't want NPCs hanging around the party at all. For example, my crazy wizard dude annoyed the ranger no end. Maybe they find GM NPCs annoying, or maybe I just run them in annoying ways.
So over dinner, I asked my wife and kids what they thought. Would they like it if I added an NPC to their party, or would they rather go it alone? My ever-pragmatic wife said "Why not give us several NPCs that we can hire if we feel like it?"
Leaving the choice in the PCs' hands - what a sandbox concept. I gotta write this stuff down...
So now I'm sketching out 5 NPCs who could be hired, recruited, or forced into joining the 3 PCs on their trek to an unknown land full of danger and mystery and nasty biting things. Because there are so many, and because I'm not forcing them to take someone along, I can make the NPCs as weird and annoying as I want. Everybody wins. So far I've sketched out a Wandering Knight of the Rose & Cross (who's trying to impress a girl), a fat coward who's an excellent camp cook/roustabout, a Spanish scholar who's perhaps too interested in monsters, and a crusty old French cartographer with a death wish. I love people like that.
*It was the early 1990s. There were a lot of ninjas back then.