Lower class heros

you are pretty much describing about half of the old school Fantasy pulp novels. Norton's 'Witch World' abounds with such characters. LeGuin's 'Earthsea' revolves around such. Elliot's 'Crown of Stars' has a couple characters with special/unique origins, but also quite a few others of no particular social note. Glen Cooks 'Black Company,' well, there are storied characters, but the company members themselves are of obscure origins. Pretty much the same story with the old 'Thieves World' series, one of the first shared worlds - a few noteworthy types (princes, potent wizards), but mostly people of obscure background.

 

Shameless self promo: I've got a novella coming out end of the month (as soon as I get the cover finalised...) that fits this. Just a regular guy who ends up in a terrible situation and has to deal with it without any special powers.

Other than that, anything written by Terry Pratchett. Also, I think most of Trudi Canavan's books fit this description as well.

 

The four principle POV characters in my WIP (the six, now seven book 'Empire' Series) are not all that special...

Tia Samos is young (late teens) highly attractive (plenty of pretty girls), intelligent, and well educated (so that she can snare a highborn hubby, bumping her family from the upper middle class to noble status). She has access to substantial sums, but these become...constricted. Tia, along with Palo Rubinus is the nominal employer of the other three characters.

Sir Peter Cortez has a muscular build (and thinning hair.) He had a noble father and a common born mother, hence he stands to inherit exactly zilch, though he did become a knight. He's also spent a decade plus fighting in a brutal war against evil that transformed him into a dang good fighter and left him a bit callous. But there are many better warriors out there, and many people with fewer scruples. He is Tia's principle protector.

Attractive, dark haired Rebecca the Gypsy is Tia's maid, bard, and female confidant. Definitely of lower class origin (Gypsies ranking about one step below dirt in the Empire). Her clan was enslaved for assorted felonies; Rebecca made a daring solo escape from captivity. While Rebecca has some street smarts, she is far from being a master thief. She is good with a lyre (and other musical instruments) but there are others with more skill. She has a few...odd talents...but no true magic.

Kyle of Bestia is Tia's hired carriage driver of peasant birth. Kyle is huge - 300 pounds, topping seven feet - but he has an assortment of physical and mental scars stemming from his time in the legions. Kyle inherited the trace of sorcery that runs through his family, with his principle knacks being Finding, Fire, and Fixing. These talents got him 'promoted' from the ranks into the 'Arcane Cohort,' wartime program that actively sought out and trained talents like him for military service - most of whom were slaughtered in droves. Kyle's military service did get him bumped from 'Plebe' (Serf) to 'Citizen' - but left him with plenty of issues 'upstairs.'

Then there is Li-Pang, who appears ever so common, but is so much more...

 

Not a book, but watch Warrior Nun. The main character is completely not prophesized or a secret heir.