Here's today's entry in the A-Z Challenge. My theme is "Golden Age Comic Book Characters with the Same Name As Modern-Day Characters."
Jack Frost -- no secret identity -- was a Timely (the original name of Marvel) Comics superhero (briefly revived in the 1970s), who first appeared in USA Comics #1, 1941. IIRC, he was supposed to be the "real" Jack Frost of legend, who came to the U.S.A. to fight crime. He can freeze things, and shoot icicles, basically.
Meet a newer Jack Frost, Gregor Shapanka, a different one from Marvel. This one was a villain, one of Iron Man's earliest foes, from Tales of Suspense #45, 1963. He later re-named himself Blizzard.
Thanks for your time.