In many role-playing games in which character creation is done on a point-buy system (Champions, GURPS, etc.), the games contain concepts called limitations and disadvantages (or something similar).
A limitation is generally applied to a character power or ability, and specifies a situation or condition in which the power isn't as effective as it usually is. (doesn't affect wooden items, damage reduced by range, etc.) A limitation can instead specify a drawback that occurs when the power or ability is used. (character takes damage equal to damage inflicted with power, etc.)
A disadvantage is generally applied to the character as a whole, and can run the gamut from the character taking extra damage from a particular attack form, being harmed by environments or substances that are normally harmless, having particular psychological quirks, having special physical requirements (a special diet, for instance), or even some genre-specific disadvantages, such as a secret identity in a superhero game.
The reason to take these game elements is that they provide cost-breaks or even free building points to add to your character. Having a power ring that doesn't affect the color yellow costs fewer character points than having one that isn't limited like that.
In every point-buy RPG I've ever played, there has been a rule that generally boils down to this: A limitation that isn't limiting, or a disadvantage that doesn't disadvantage the character, isn't worth any points. The best example I've seen is a character with a 'cosmic awareness' power that allows her to know pretty much everything about whatever she's concentrating on, and then tries to get building points back by taking the disadvantage 'Blind' -- if her cosmic awareness provides all the information that her sight would normally provide, then being blind really isn't limiting to the character, since she can just use cosmic awareness to get the information she'd normally get from her eyes.
However, there are some situations where a disadvantage or limitation seems limiting, but really isn't, based on the full suite of other abilities or powers the character has purchased. These kinds of situations can provoke arguments between players and GMs based on whether the character's limitation meets the criteria for the 'not limiting thus no points' rule.
To avoid these arguments, I've come up with a concept I call CITS (Character Individuality Too Severe); if a character has a disadvantage, but always seems to be able to use a power or ability to avoid the effects of the disadvantage whenever it's presented, I'll declare CITS on the character, reducing the point value of the disadvantage to zero, and consuming experience points (or whatever in-game currency is used for character improvement) until the amount of points gained from the disadvantage is 'paid off'. To avoid this ruling, the player must describe some situation or set of situations in which his powers and abilities would not be able to avoid the effects of his disadvantage. (In other words, the player has to explain to me, the GM, exactly how to trigger his disadvantage.)