Flint Paper is the freelancers' next-door neighbor, a stereotypical private detective. His work method often consists of "pummeling", and he has, to date, proved to be effectively indestructible.
Flint's appearances are typically brief ones at the start of a story, with Sam & Max passing by his office while he's in the middle of pummeling some cheap thugs senseless. In Sam & Max Season Two he actually has a small part in the plot, investigating Bosco on behalf of what turns out to be Ms Bosco. In Sam & Max Season Three he appears in the first episode eating spaghetti in Stinky's. Girl Stinky planned to murder him with an axe, but, after Sam & Max gave him a hard hat, he noticed some peanuts on the spaghetti, thanks to the light of the hard hat, and, while going to Girl Stinky to complain, the axe hits a seat instead of Flint. Previously, a future vision showed Flint Paper delivering the Power Core to Momma Bosco, but, later in the game, Sam & Max will be the ones to discover it. In Season Three, Sam would sometimes examine him in a way where he would talk about him as if he was a narrator in a private investigator noir story.
A mainstay if there ever was one, Flint Paper's office has been next to the Freelance Police's since at least as far back as Monkeys Violating the Heavenly Temple and in all incarnations except (possibly) the animated series, which he curiously is never mentioned in.