Try stuff by Nexon. It's a South Korean based company that makes MMOs with micro-payments, and they have quite a few different things: Maple Story, their most popular and easiest, Mobinogy, (or something like that) which is like a 3D Runescape, minus the suck, Dungeon Fighter Online, an arcade style beat 'um up, but in MMO form, a few little games that a basically flash games, and Combat Arms, which is kind of like Counter Strike, but with some slight differences. The micro-payments are mostly cosmetic stuff (such as a different look for your avatar or weapon), and it's completely free and full, even if you never spend a cent on them. It doesn't shove it in your face either, which is nice.