Rory did a great job listing the problems with many flaw-based systems: they encourage min/maxing and don’t necessarily add a lot of fun. I decided to see if I could come up with a flaw system that would increase table fun.
Rule 1: Flaws shouldn’t make your character be useless in combat. If they have any combat effects at all, they should increase randomness and/or wackiness.
Rule 2: Flaws should support archetypes. Feats and other character abilities are meant to build larger-than-life heroes. When possible, flaws should do this too. They should be reminiscent of existing play styles and/or literary heroes.
Here are my flaw rules:
If you decide to take an attribute at a value of 8 (a dump stat), you must choose a flaw in that stat. If your lowest attribute is 10, you don’t need to take a flaw. (Players who take an 8 are often aware of their dump stat and often play it for laughs anyway.)
You get rid of your flaw if you ever raise your stat to 10 (so, by epic level at the latest).
Civilian: The first time you make a melee attack in any encounter, your spastic unpredictability gives you combat advantage. However, any time you miss with a melee attack, your opponent may choose to automatically disarm you as a free action.
Feeble: You can’t carry heavy items (or wear heavy armor, or your own share of the supplies). Even if your group doesn’t track encumbrance, you should insist that your burden feels so very heavy.
Puny: You have the same weapon restrictions as a halfling. A halfling with this flaw must use all weapons two-handed.
Can’t swim: If you can’t reach the bottom of the water with a toe, you’ll start to drown. You are probably also afraid of water.
Can’t climb: Someone will have to rig up a rope and pulley system to get you up cliffs. You are probably also afraid of heights.
CONSTITUTION FLAWS (not that anyone ever takes 8 Con, since it is used for HP)
Medicine dependent: You require a daily dose of drugs and potions to avoid being Weakened. You occasionally cough blood into a handkerchief.
Chronic disease: You contract a minor disease, using the disease track, whenever you are Bloodied or wet. Symptoms of the disease include a hacking cough and a -5 to all Strength and Constitution skill checks. You occasionally cough blood into a handkerchief.
Slow: You must make an easy Endurance check to run. If you fail, you take a normal move action, at the end of which you must put your hands on your knees and pant.
Mind stronger than body: After using your highest-level Daily power, you are Taxed (a new condition which means that you are Slowed, you talk with difficulty, and you press a hand dramatically to your forehead). This condition lasts until you receive any form of healing. Also, you occasionally cough blood into a handkerchief.
Allergic: Choose a substance, creature, magic, etc. which causes you to sneeze helplessly. While exposed, you must make a saving throw each turn or spend a minor action sneezing. Your allergy acts as an early warning system, causing you to sneeze before the substance could otherwise be sensed.
Old: You have one less healing surge than usual. During every extended rest in which you spend a healing surge, you must make a saving throw or say “I’m getting too old for this” or talk about your old bones.
Bad aim: On a natural one on any Dexterity-based attack, you must repeat the attack, with an ally as the target. If no ally is in range, you may target an enemy other than the one you missed.
Bull in a china shop: You must make a saving throw to not break any adjacent delicate item (-2 on the save if you are holding the item).
Large: You are fat or musclebound. You must make an easy Dexterity check to squeeze. You need an unusually strong mount. You must make a Thievery check to do any action that requires fine motor control.
Butterfingers: On a natural one on any skill check involving tools, you drop your tools. On a natural one with an attack, you accidentally throw your weapon or implement. If it’s a melee weapon, you must make a melee basic attack on a target of your choice within 5 squares that is not adjacent to you.
Illiterate: You may or may not be able to write your name, but that’s the limit of your learning.
Hulkspeak: “Kradgar not happy about pig man behavior. Kradgar SMASH”, etc.
Uneducated: You say “ain’t”, use double negatives, etc.
Punchdrunk: You talk like Rocky.
Forgetful: You must make knowledge checks to remember known names and facts if you didn’t write them down.
Crazy like a fox! You think every plan is good, and immediately put it into execution. (This flaw comes standard with ratling PCs.)
Overconfident: You think each of your bluff, diplomacy, and intimidate checks is wildly successful.
Blind: You gain Blindsight 5.
Bumpkin: You have a -5 to streetwise checks. Furthermore, everyone in the city knows you’re a sucker.
City slicker: You have a -5 to Nature checks. Furthermore, all of your failed Nature checks lead to inconvenience or danger: unsupervised, you gather bouquets of itchflowers, pitch your tent in quicksand, and catch poisonbunnies for dinner.
Spendthrift: At the end of each adventure, you insist on getting your full share of the loot. However, at the beginning of the subsequent adventure, you are somehow down to 1d10 gold.
Over honorable: You don’t know when to conceal the truth, and you take offense in the most inconvenient situations. You must keep your word, and may even start the game with an inconvenient vow.
Tempted: Choose a temptation: food, wine, love, etc. When presented with your desire, you must make a saving throw in order to keep yourself under control.
Ugly: When not wearing a hooded cloak or helmet, you have a -2 Diplomacy penalty and +1 Intimidate bonus. Odds are, you are hopelessly in love with someone very beautiful.
Mean: Or haughty, abrasive, or bossy. You have a -2 Diplomacy penalty when dealing with equals and superiors. You have a +2 Intimidate bonus when dealing with those weaker than or subordinate to you.
Mute: You might alternatively have a strong accent or speech impediment. You communicate through semi-intelligible speech or signs. You must make a Diplomacy check to express complicated thoughts to strangers (luckily, the other PCs can understand you fine).
Shifty: Whatever you do, people assume you have an ulterior motive. Maybe it’s the pointy mustache or sinister cackle?
Foot in mouth: You always accidentally say the wrong thing. Furthermore, you ALWAYS try to Aid Another with Charisma checks. You must make an easy Wisdom check to avoid giving away secrets.
Cross-Attribute Flaws: If someone wants to take a flaw from an attribute they’re not weak in – for instance, they want to be illiterate but smart, or blind but perceptive, they should be allowed.