Without really meaning to do it, I've found that Tennibrook Balmossie, who's become my favorite character, has a few personality traits that recur frequently in roleplays and manifest as character flaws:
1. She's too honest. She's almost congenitally incapable of guile and keeping secrets.
2. She's very ambitious. She's almost never satisfied being where she is, even by the standards of vulpines, who in theory should be practicing the Second Tenet, self-improvement, as part of their religion.
3. Tenni is dutiful almost to a fault, sometimes at the cost of her personal life. Her relationships sometimes get neglected in the name of work, work, work. Then she needs to take a few days to catch up with her friends.
What are some of your characters' biggest flaws?