The Tailgater is Obey's four-door luxury saloon from GTA V and GTA Online, due to appear in Grand Theft Auto VI. Its styling appears to be drawn largely from the Audi A6 (C6) with grille and detail cues from the A8 (D4) and fender bulges reminiscent of the RS6.
Vehicle data via GTA Wiki (Fandom), CC BY-SA 3.0.