though I can name you several better yanderes... ie: School Days's Kotonoha
because it is the normal ones, with no special abilities (like Yuuno), the girls who check your cellphone messages and send you pictures of herself in the nude, who WANTS you to look at them, and NOTHING other than them, who checks your internet usage, sites visited, cache deleted, and goes through your dirty laundry to find stray hair...
then again MANKOTO totally enjoyed his travesty blaise~ didn't he? That said, Yuuno comes in close second in my book, simply because her anime is only now being shown.