Favourite - As far as creativity goes, probably Bohemian Rhapsody since it's a pretty out of control nature and unique ability, plus whilst I have some problems with the way it was countered, I at least like that it had the whacky element expected of JoJo and can even be seen as poking fun at overpowered Gary Stus and Self Inserts.
As far as which one would be my favourite to have, either Heaven's Door, Killer Queen Bites the Dust or Pearl Jam. I don't think I need to explain why these two would be ridiculously beneficial.
Design-wise, my favourite would be either Killer Queen or Made in Heaven.
Least favourite - When it comes to both how they're utilised and how they'd work if I were the user, either Highway to Hell or Dragon's Dream. The former is only useful if the user is suicidal and the latter relies on such an abstract and situational concept as Feng Shui.
Design-wise, it would be a cheap move to go with those that don't have a physical design, so I'll go with Strength because it's just a fucking boat.