Indeed, but I had to keep the word entry to a workable length.
In Italy I came across a (leftist) samizdat bulletin where every article carried a byline that was a variation on the name Paul: Paolo, Pavel, Pablo, Pawel, Paulus, etc. It wasn't hard to track down the guy responsible - he had a nightly round of wet-your-whistlestop 'declamations' at pubs - and he turned out to be a fascinating character indeed.
As I suspect you already know (but for completeness sake), in addition to John, Juan, Giovanni, Johan, and Johannes, there are also these variants:
János, Ivan, Hans, Sean (and Shawn/Shaun), Shane, Jonas, Ian, Evan, and Owen. There are also several that are men’s names in Europe, but are women’s names in America: Joan (as in Joan Miro), Jann (as in Jann Wenner), Jan (Jan Stenerud), and Jean (as in Jean Jacques Rousseau). The link lists a few dozen more that most people probably wouldn’t recognize.