Build a
duellist, build it well!
Naaa, I'm just kidding, only an idiot would try to build a duellist.
They get crazy initiative, but nothing to do with it except stand in front of people and look pretty...
They get crazy AC, but only after they've survived to high levels where it doesn't matter anymore...
They get crazy movement abilities, but no speed or sneak attack to capitalise on it.
Basically they make a dex-based AC tank dexier and more AC tank. By denying you the use of armour or shields you lose all hope of defensive magical enhancements, so your AC is the only thing keeping you alive. And with nothing but dex, intelligence, and defensive fighting to give you AC, you can all but guarantee that you won't be doing any damage. Its only real value is to people whose monks always die...
Naaaaa, I'm kidding, duellists are great, I made one and the DM was constantly trying, and failing, to kill them. They finally died after literal rock, literally fell, and literally everyone(important) died...
P.S.
How do skill points and multiple classes work? If I have a level 1 rogue, and disable device is a class skill, so I take 4 ranks in it, and then I take a level of commoner, and it isn't a class skill anymore, but I take a rank in disable device anyway!
Then I am a level 2 character. What are my maximum ranks in disable device?
A:5
B:2+1/2
C:Something else that you made up to feel smug.
How expensive(in skill points) will that 5th rank be?
A:1
B:2
C:Your 5th rank is currently lost in space and will not be available until it has exhausted the supply of zucchinis.
P.P.S.
What if, as a trait, I want to reduce my skill points per level by 1(4 at 1st) to add one(or more?) skills to my list of class skills? Say that it can reduce you to 0 skill points per level to scare off the 6 int orcs...
It is bad because:
The party fighter was just going to blow those points on jumping, but now they have full use of use magic device and can reliably use scrolls of righteous might and shapechange while faking their alignment to wield the Lawful Evil intelligent scythe that was meant to be the villain of the campaign...
By trading 1 skill point to gain a class skill you haven't lost anything, because the skill points spent on that skill are worth twice as much as they would have been otherwise.
It is good because:
The party fighter decides that they want spot instead of ride and handle animal. They lose the points that they would have spent on handle animal, and move the points that they would have spent on ride into spot. Now they don't fall into a barely-concealed pit trap or rent for 15d6 sneak attack damage by a troll rogue every time that they lead the party. The player is happier but when the party has to travel 200 kilometres(and 5 levels) by horse the fighter is constantly reminded that they don't have the skill points to learn to fight without dismounting at the start of every encounter...
They most certainly HAVE lost something! 1 skill point per level! I mean, who buys more than a single rank of a cross-class skill? Wizards? Bah, even with 20 odd intelligence they still have less points than a rogue, and those certainly never have enough skill points!
The character will trade the maximum number of skills that they can apply full points to to increase the number of skills they can fully utilise. It is versatility with a relevant cost, which is what traits are all about. Also it is easy enough to double the costs, or add a fixed loss of skill-points at 1st level...
Example:
Methodical
A place for everything and everything in its place. Inconsistencies in an environment just stick out at you. Although you are often too busy sorting things to practice your other skills...
Benefit
Search is a class skill for all classes that you take.
Drawback
You gain 1 less skill point per level (four less at first level). This can cause you to gain no skill points from a level, even though you would normally gain a minimum of one.
Roleplaying Ideas
If a character has this trait then they might insist that things be treated in the correct manner. They tend to be frustrated by chaotic alignments.