Not to be too literal about "leaping," but the trip I took to Germany as a teenager. On my own, without any family, for the first time ever. I was going to be staying with people I didn't know (aside from Carola, who my family had hosted the previous spring) in a strange place. At least I knew the language! That summer turned out to be the greatest thing I ever did, changed my whole life, but if I'd been afraid to do something drastic, it would never have happened.
Other leaps of faith: deciding to go down to Georgia, getting into Reiki, quitting my job to do freelance.