I use a variant Thief class in my campaign called the Scout. The Scout is the Greyhawk Thief with the serial numbers filed off. They can be Lawful, use a light shield called a buckler (+1 vs 1 opponent only, ineffective against missile fire) and missile weapons. They progress in steps of 4 levels in combat, and roll saves as magic-users.
So, why not just use the Thief? Thieves, by both name and alignment, have an implied mandate to steal from other player-characters. In addition, I do not allow Chaotic or Evil player-characters IMC. This is for a variety of reasons, chief among which is I just don't find refereeing evil characters a fun way to spend my time.
I've imagined the Scout class (complete with level specific names) to be agents of good trained in arts generally not known among members of polite society. My inspiration was a variety of characters who skirt the bounds of good and evil in an attempt to protect others: James Bond 007, Batman, Robin Hood. These types look into the abyss every day and struggle to keep the abyss from looking into them.
At any rate, there has been some discussion around 'web lately regarding thief skills. It is said they're next to useless at lower levels and I find myself in agreement with this opinion. Historically I've merely boosted the chance for success but I've been rather unhappy with the results. One variant I've recently envisioned is using the basic mechanic inspired by the "climb walls" skill.
Greyhawk lists the chance of slipping while climbing sheer surfaces to be 13% or, to turn that on its head, and 87% chance of success. The probability of rolling 2-6 on d6 is ... 87%! I've thought this could be applied to all the Thief/Scout skills through 4th level. Upon gaining 5th level, success would be a result of 2-10 on d10 (90%), changing at 9th level to 2-12 on d12 (92%). No matter the die used, the result of "1" would always be a failure.
The only mechanic I'm dithering over changing to this degree would be lock picking.
What do you think? As a referee I don't think being able to reliably sneak and hide is going to create a class of uber-ninjas but I'm interested in what others think about this.