The Bullet GT is a supercar featured in The Ballad of Gay Tony. The Bullet GT is evidently based on the Bullet, a similarly designed sports car from Grand Theft Auto: San Andreas, sharing similar Ford GT-like design cues and hood scoop. The player can spawn the Bullet GT in front of him by dialing this cheat code: 227-555-9666.
The Bullet GT has a massive top speed, and is plausibly and argueably now the fastest car in the game, butting heads with the Comet. It can turn corners easily, and barely has any understeer.
Its make is unknown, but it may be a Vapid, as Vapid is based on Ford in the game, and the Bullet GT is based on a Ford GT.
Hence it's referable name "GT", the Bullet GT is based on a late model Ford GT, and the back of the car resembles a Lamborghini Miura due to the Window Shutters.