Winston Payne, known as the "Rookie Killer", is the first prosecutor you face in every game of the series. He also shows up in GS4, and you can see his new profile, here.
 

Personality: Like all the prosecutors Payne has a superior attitude, but that fades quickly when he faces actual opposition. Not the best prosecutor of the bunch.

Misc Facts: He lost his hair in a case against Mia Fey. The shock of losing blew it right off his head.

In the first versions of the GS script, Payne was originally going to be a defense attorney - Phoenix's lawyer, in fact, who would defend him against an older Edgeworth in the Turnabout Sister's case. But when The First Turnabout took over as the beginning case, he was moved to prosecution.

Friends and Family: The lately released GS manga mentions that Payne has a wife, and it's intimated in GS3 he may also have a daughter.

Name Origin:
English: "Winced in Pain" was taken to match the Japanese name.

Japanese: The name "Auchi" is a Japanese Romanization of the English word "Ouch." It's also claimed he was named after a dentist of one of the staff members.

French: A boulet is a person who always does things incorrectly.

Background:

Larry's Ex-Girlfriend, and the victim in Phoenix's first case.

Personality: Mostly unknown.
 
Misc Facts: None.

Friends and Family: She was dating Larry up until case 1.

Name Origin:
English: "Cindy Stone" may have come from "Cinder Block."

Japanese: "Takabi" comes from the Japanese phrase takabisha, which means "to be on one's high horse."

Background: Nothing especially.

A witness from Phoenix's first case.

Personality: Slimy. He can suck up a great deal, but in the end is a common thief and coward.

Misc Facts: That's not his real hair.

The mole on his forehead was added as a mark of guilt.

Friends and Family: Uknown.

Name Origin:
English: "Sahwit" comes from, "Saw it," as he is an eyewitness claiming to have seen the crime being committed.

Japanese: Yama no Hoshi literally means "star of the mountain," but I'm unsure of the reference. But in case one he does quote the saying, "If there's a mountain, someone will climb it" in reference to him being compelled to peek at Cindy's crime scene.

French: Comes from Frank qu'a vu meaning "Frank saw it."

Background: Nothing especially.