A while back I talked about Brown M&Ms, small things that you can look for that reveal that there might be problems with the larger system. I was doing chargen for something this weekend when I spotted something that was very much a brown M&M for me: the driving skill.
You can tell a lot about a modern game by how it handles driving. As a fairly ubiquitous skill (at least among adults in a modern American setting) it is actually an anomaly to find a character who can't drive, but such characters do exist, so it's necessary to account for them. At the same time, you will have characters for whom driving is their thing, and they need to be effectively distinguishable from people who are just basic-competency drivers.
That's a tricky problem, and most of the solutions for it are pretty awkward. For example, one option is to make it mandatory that everyone buy the driving skill to whatever the system considers competence(assuming that the descriptions match the reality of the dice) but that kind of sucks for players who are usually already a little squeezed for points.
You can address that by giving basic competence level in driving for free, but what about the guy who can't drive? Does he get to use those points somewhere else? Plus, have you just made it much cheaper to make Driving Guy than Shooting Guy?
Then there's the classic "Everyone can drive, but you only need to roll the dice when doing something dramatic, like a chase or the like". Now, I love this sentiment, so why is it a brown M&M for me? Because if this approach is the exception rather than the rule in a game, then there's a problem. Are you rolling for boring things with other skills? Have you thought about what other skills can do without rolling? I think this is a great approach if it's the approach for all skills, but otherwise, it's a lazy solution.
Now, for all that this is a sticky problem, there have been games that have handled it well. Over The Edge had a default competency level of 2d6 for things that common sense said you should be able to do (run, drive, jump and so on). The nWoD system makes you buy it, but makes it cheap to do so because (unlike many other systems) the first rank of a skill conveys fair competence, mechanically. Systems that let you default to using just stats for such rolls offer a somewhat half-assed solution, but it's better than nothing.
While driving is really iconic for me, it's not the only skill that runs into this problem. Pick any game with a skill list and consider which of these anyone could do. The whole athletics category jumps to mind, but there can be other fun things like reading and writing which can also get a little weird.
This can seem like a very small thing, but it's exactly the sort of detail work that makes up the hard 20% of making a game sing. Just something to bear in mind.