I'm super in love with everything Scott Pilgrim, from the graphic novels to Scott Pilgrim vs. The World. (I even named my hedgehog "Knives" after Knives Chau.) Then I saw that someone had made the scarf Knives wears when she's fighting and was just like "Psh, I could do that."
The only thing I don't like about mine is that I think I did the blocks too long before switching in between black/white, but I'm just going to say that makes mine special and call it a day.
In black yarn, cast on 20. Knit a row, purl a row. Repeat until you've done 32 rows total, if you want your scarf to look like mine, or do like 20 rows per color if you want it to look more like it did in the film.
Switch to white! Knit a row, purl a row, until you've done the same number of rows as you did for the first block.
Switch again! (You get where this is going? Just keep going and switch every x number of rows. Go until the scarf is the length you want it, depending on your height, which should be around your knees when wrapped once around your neck. End with a black block.)
Bind off! Weave all the annoying little strings hanging off into the scarf.
You're done! Go fight stuff!