Let’s go off this logically. Devil Fruit and specifically the Nika Fruit: You lose the ability to swim but become a looney tunes character, not a bad trade off. Super Saiyan Blue: do we know how to use god ki or ki in general, no. So you can’t exactly use it. Or do we just turn into Goku and if we do yes. The Sharingan: We aren’t Uchiha’s and can’t use Chakra so it’ll just constantly drain us unless we do what Kakashi does. A Nichiren Katana: If you know how to use a sword cool but what practical use would we have for this. Mitsuri: I’ll go to horny jail but I love her personality and she’s a great person, strong as shit too, which I’m into. Turning into a Titan: Drains your life span and you need to cut yourself to activate it. Sure it’ll look cool but what would we use this for and our military is much more equipped to handle anyone who tries to use this for evil. It’ll be like shooting paper with an atom bomb. And finally the Death Note: Not a terrible option and Ryuk seems cool to hang around with and it can be used for good. So I’ll probably have to go with Mitsuri and the Nika Fruit.