Any job where you're expected to talk complete strangers on a sales floor into buying something will challenge your SA, so a job in retail clothing sounds like a good job if you want to challenge yourself. (Counter positions, like fast food, are less of a challenge socially, though the pace is typically faster.) I did floor sales as part of my job for 13 years. On busy nights, I'd have to strike up conversations with dozens of complete strangers (most of whom had no desire to talk to me).
You might also consider volunteering if you're just looking for a challenge and don't depend on the money. A lot of volunteer positions revolve around socializing, such as with children, the elderly, in hospitals, etc.
For forty-seven years I've put up with it now. I must stop Christmas from coming ... but how?
I did this for a while and its really a ****ty job, but I found it was the perfect amount of social interaction and pushed me out of my comfort zone a bunch of times, and resulted in building my confidence.
Yeah I'd say delivery, that's the main job I've ever done.
And all our yesterdays have lighted fools the way to dusty death Out, out, brief candle! Life's but a walking shadow, A poor player that strut's and fret's his hour upon the stage and is heard no more, It is a tale told by an idiot, full of sound and fury, signifying nothing. - Macbeth