Lol, sorry, i never read death note, but from the looks u love one piece so i aint know what to say, but was suprise nami is one of ur fav, she is kinda. somewhat..........useless
You should not mistaken cowardliness for uselessness. I dare say Nami is on of the most important people on the ship. She is the Navigator, and she is responsible for all the traveling, without her, both Going Merry and Thousand Sunny would never reach the places they reached. Not only that, she is probably the best navigator in the world, with her astonishing talent to draw maps, known the winds and the sea currents, and most importantly the weather, even the Grand Line's weather.
And if she was more confident on her fighting abilities and if she was braver for more than mere few second, you'd have one of the top fighters around. It would be hard to say if she could beat Luffy, Zoro or Robin, but if she was to fight at the top of her abilities, she would indeed put up a fight.
Not only that, she is really beautiful, and I really like her. I wouldn't mind making her my personal character, but I disliked to, a certain extend, her short hair, and even her bright hair, for it didn't suit the look I was looking for, but yet I still love all those things about her, and Oda just nailed it.
Ps: You should try the Death Note Manga.