Flaw 1:
Uncontrollable Phasing
You will, from time to time, randomly disappear from existence for a short period of time. You then, after a certain amount of time, phase back into existence with no memory of anything that had happened in the time of your disappearance.
Effect: While phased from existence, you can take no damage or be attacked, as you no longer exist, but you become Shaken for as many rounds as you became phased for from your experience being literally non-existent. This number of rounds is determined by the DM and can happen anytime at the DM's discretion.
Roleplaying Ideas: Does becoming unreal change your character in anyway? Do they become enlightened from what they experienced? Do they become unnerved? Terrified? Angry? Did they see/hear/experience something while out of existence? Did they learn some form of knowledge from the encounter? Some Truth?

Flaw 2:
Hauntings of the Past
You have disturbing Dreams, often reliving past events, often resulting in emotional weakness.
Effect: You are known to have dark dreams, often representing an unpleasant past event. Every 1d6 days at night (basically once a week at random), the character has an upsetting dream. Upon waking, s/he becomes shaken for the next six hours. In addition, on the night of the dream the character must succeed an additional will save of DC 15, or make loud noises (Talking in sleep, or Screaming), this may at DM's discretion wake both the player and/or other party members interrupting their sleep for 1d3 hours.
Roleplaying Ideas: The PC can use this to clue in party members to their past event. Party members who listen to the pc talking in their sleep may figure out clues to the pc's past.

Flaw 3:
Directionless
You have no sense of direction, you cannot get anywhere without the help of a map and compass, or someone else. Directions are useless to you. Even setting out more than 5 feet you become obliviously lost.
Effect: -4 to Survival checks, you are unaffected by any know direction spell or spell-like ability, and it takes twice as long to travel anywhere without the help of a compass and map, or traveling with someone who is competent enough to help guide you. On the other hand from all the wandering and traveling of being lost your body is more durable.

Flaw 4:
Magic Corrupting Touch
You corrupt magical items that you touch.
Effect: A magic item that you touch, wear, or otherwise utilize for the first time has a 25% chance of becoming cursed. This roll is made in secret by the DM. If the item is cursed, the type of curse is chosen at random or selected by the DM. If the item was cursed prior to you touching it, that's too bad, it has two curses now.
Roleplaying Ideas: How did you acquire this curse? Maybe you stole from the wrong emporium, or drank one too many potions.