It's also shout by Dio after delivering the finisher of his ZA WARUDO (a.k.a. "The World") supermove. Paired with a leaned-back, knees-bent, pseudo-pelvic-thrust sort of stance (think DBZ-style power-ups in the other direction).
The twenty (20) "Y"s are derived from the stick figure Flash animation (see: post #107964) that made the move all the more infamous across the Internet.
Dio's son, Giorno Giovanna, also uses this battle cry.