(still catching up…)
I’ve got a few options here.
In my Karameikos campaign, they still talk about Grygory, a guard who accompanied them on a decoy caravan to try to draw in the raiders who were threatening the mountain pass. The caravan was ambushed by gnolls, and Ivan the other guard was pretty much taken out by the first arrow, so he just had to stay under cover. But Grygory proved a crack shot with his crossbow – he rolled incredibly well all night and seemed to hit everything he aimed at. So now he has been elevated to the status of legend within the group.
Also in my Karameikos campaign, Clifton Caldwell features a lot…but I’ll leave him until the next question…
But my personal favourite, even though he only featured briefly at the start of the first session for the group who literally fell into my campaign, was Druht, a depressed mud mephit that they pretty much landed on, who gave them a bit of information about the world in the way Marvin the Paranoid Android probably would have done, and then disappeared into the mud when the lizard folk appeared.