Any iteration of Jack Frost :D
No, but really, in all seriousness, Liam'O Brian is always great as Akihiko, Junpei is my favorite Role Vic Mignogna has ever done and in General, all the P3 Cast had great VA's. Yes, even Fuuka's had her own unique charm that I prefer over her portrayal by Wendy Lee in her modern appearances, who just sounds generic as hell >:(
Teddie and Kanji are great, no matter who they are...Kinda wish Naoto's Original VA wasn't screwed over and had to be mysteriously replaced come Ultimax and PQ...it's not that different sounding, best P4 Girl just isn't that same now...
As for P5, Mercer was so good as Yusuke, I couldn't even tell it was him at first! Jamieson Price was great as Sojiro, as he is an everything, same goes for Richard Epcar as Kobayakawa-Banana-Boi. "Igor" was great as well.
Keith Silverstein was great as Shido, then again, Silverstein typically excels at two kinds of role: The Handsome but lovable Bastard and the Total Douche...Shido was obviously the Latter, lol.