Ramjet is the name of several fictional characters in the various Transformers universes. All have been Decepticon aligned characters who turn into jets, usually white.
Ramjet made regular appearances during the second season. In episode 33, "Auto Berserk" he took part in the air raid on the Autobots' column escorting the Negavator. Megatron ordered to his jet 'Cons to divert the 'Bots from their device so that he could seize it. But Smokescreen used his smoke so as to dazzle the Seekers, and then downed them all, including Ramjet, with his disruptors. Meanwhile Megatron was sitting already in the Negavator's cab. But he had no time to destroy the Autobots because Ramjet fell just on the cab and knocked Megatron out of it. So the Decepticons had to get nothing for their pains again. Ramjet's most notable appearance, however, was in episode 40, "A Decepticon Raider in King Arthur's Court" where several Transformers characters (Starscream, Rumble, Ravage and Ramjet himself) were somehow transported back in time to England of the Middle Ages. During this episode, Ramjet made good use of his name by head-butting a knight. He also participated in a jousting contest, with Rumble atop his nosecone wielding a lance against Spike Witwicky mounted atop Autobot Warpath's turret. After this tournament he together with Rumble helped Starscream to gather all the necessary ingredients for making the gunpowder which the latter wanted to use against the 'Bots and their human allies. At the end of the episode Merlin helped both the Autobots and Decepticons to return to their own time.In the original Transformers series, Ramjet appeared in Season 2. He made his first appearance in episode 30, "Dinobot Island Part 1." How Ramjet came to Earth was not shown.
Ramjet made brief appearances in The Transformers: the Movie - firstly as the Decepticon shot down by Optimus Prime during the battle of Autobot City, and secondly during Unicron's attempted destruction of Cybertron.
After the movie, Ramjet was thrown against a building and seemingly destroyed by Ultra Magnus, but returned to make small appearances throughout the third season.
One possible explanation for all of Ramjet's deaths may be that the "Ramjets" that died were merely Decepticon "drones" that looked like the original Ramjet since there have been Decepticon "drones" that appeared similar to Thundercracker and Skywarp in the cartoon before.
He last appeared in "Thief in the Night".