I propose a permanent cosmetic purchase. IE: It unlocks for the account the ability to gain access to a new hair style or unique color. Or maybe some different facial hair. Once you unlock it for your account, any character you make can have access to it through the typical hair/color changer. Why an unlock for account and not just character only? To tap into that sweet cash from people who don't like the idea of spending money only to lose said thing upon death or theft. Through this you could come out with different colors, styles, and make each one cost a good amount like... eh... 5 dollars? Maybe more depending on how whacky or unique the color/style? Or even make it mystery and make the style/color you get random, much more unique styles/colors having a lower percentage to get.
Edit: Orrr, just for one character, since that fits the overall theme. Though I really think an account unlock would result in more purchases ya know?