#1 The New Age Outlaws

Oh, you didn't know that the Outlaws were a thrown-together team? You just better call your Internet provider so you can use the WWE Network to re-watch Monday Night Raw in the spring of 1997 to see the feud between Billy Gunn and Jesse James which led to a seemingly-doomed summer pairing.
Rather, don't, as the two men feuded first over who would "get" to have Honky Tonk Man provide his managerial services, then continue to battle over the fact that Honky turned on heir apparent Jesse James, a.k.a. "The Real Double J," so named because he was revealed to be the true singer of "With My Baby Tonight" in a Milli Vanilli-inspired angle.
Gunn, in winning Honky's services, was redubbed "Rockabilly" heading into the summer of 1997, and then...nothing. James and Gunn were lost in the shuffle of WWF focusing on The Hart Foundation, Steve Austin, The Undertaker, and the impending invasion of his long-lost brother, Kane.
In October 1997, Gunn and James's pairing came down to the latter simply suggesting that their careers were going nowhere and they might as well team up; Rockabilly's response was to smash a guitar over his now-former mentor's head in an ode to Honky Tonk Man's favorite form of assault in the 1980s.
From that point on, The New Age Outlaws' heel antics, sing-along entrance, and embracing of pop culture phenomena like South Park helped cement the Attitude Era staple of the "cool heel" brought on by Steve Austin the previous year; from that point on, the Outlaws captured five WWF Tag Team Championships (and a WWE Tag Title in a brief nostalgia run as part of the Authority storyline during The Shield's babyface turn), becoming onscreen and front-office staples in the process.