DeathPaladin brought up the interesting Deadly Sin system from White Wolf's World of Darkness tabletop roleplaying game. Now, the World of Darkness games obviously have a lot of mechanical systems involved with the sins (and Virtues as well, actually), but that's part of their whole gothic-fantastic nature. (The games used to be called gothic-punk, but White Wolf later ditched that description.) These games are probably best known for their vampires, but White Wolf's systems span all kinds of different monsters. This Sin idea is replicated across many of them.
While there's many different examples of methods for fleshing out your character, I actually really like the Deadly Sin game. Applying an archetypical behavior and flaw to your character gives you a "roleplay button" to spam whenever you feel like you're torn on your character's proper reactions.
Let's take a look behind the jump and see how we could use the Seven Deadly Sins in the context of our World of Warcraft. (For the record, the Seven Sins we're going with are Lust, Gluttony, Greed, Sloth, Wrath, Envy, and Pride.)