Supernova
From Superdickery
Supernova was introduced in 52 and his identity was presented as a mystery. By the time they actually revealed his identity about 6 months later, just about everybody and their Aunt Suzie had figured out that it was Booster Gold in the costume, save the desperate few who clung to the theories of Ray Palmer, Conner Kent, or, weirdly enough, John Henry Irons. As someone on LiveJournal put it, "Only in comics could they reveal Supernova's true identity to be someone who's been in the same place as him, at the same time, on more than one occasion - and have that be the most obvious candidate."
Supernova's powerset remains something of a mystery still. Teleportation is involved, and the costume gives off light, both of which are somehow or other connected with the Phantom Zone projector technology being integrated into the suit, but Supernova has demonstrated other powers not explainable by those means, and Supernova/Booster has been shown or mentioned to have stolen several other things that were presumably used in the creation of the suit. Time travel is a nasty, nasty thing. Apparently it also has lasers and some size-changing tech.
An interesting aspect of Supernova is that the costume is keyed to the Carter genetic code, which means that being related to Booster Gold is a prerequisite for Supernovaship.
Supernova I was Booster Gold, having faked his own death to operate for Rip Hunter without Mr. Mind noticing within the pages of 52. He was Supernova from about Week 8 or so to Week 37.
Supernova II was Daniel Carter, Booster's ancestor from the present day whom Mr. Mind had trapped in Rip Hunter's lab in Week 19. He was Supernova in Week 52 up until about 2 months afterwards in Booster Gold #1, when he got himself sucker-punched and the suit itself stolen by...
Supernova III's identity was originally a mystery, but was revealed in Booster Gold #4. Popular theories included Booster Gold (yes, again, though phrases like "from the future" or "from a different world in the Multiverse" were usually added.), Rip Hunter, Conner Kent, Ted Kord, and Jonar Carter (Booster's father, although only HotAndCold and Fishy even really thought this was a possibility). Supernova III turned out to be Jonar Carter. This is why you should always listen to HotAndCold and Fishy when it comes to Booster-related things. Jonar has been Supernova since Booster Gold #1 on.