Four years ago I would have said Josuke, but today I lean on Giorno or Jolyne, really can't decide. I love Giorno's design the most of all Jojo's, and Gold Experience is pretty cool. I like his backstory and upbringing, as he was close to going down the same route as his "father". He's a polite and kind gangstar who can deliver a brutal beating.
Now for Jolyne, she's a strong, sexy, independent woman who makes pretty good use of her seemingly weak stand. I personally thought she was the most hardcore Jojo of them all.
It's a real tough decision for me, and who knows, maybe part 8 Josuke will take the spot of best Jojo since he's made himself my third favorite Jojo.