I like the simplicity of BRP's percentile-based skill system. (Chaosium's Basic Roleplay, or BRP, is the system behind Call of Cthulhu and Runequest, among others.) It makes it trivial for new players, even ones that just walked up at a convention, to pick it up and go.
The problem I have with it is that I always hate how it makes you basically min-max your skills, because you need a very high skill to be able to rely on it.
Here's an example - one time, I was given a race car driver pregen character. He had a 60% Drive score, which seems decently high. However, in practice, once I was chasing some guy in a car, I'd go to make a corner and the GM would say "roll Driving!" in the 4 in 10 chance I'd fail, I'd wreck into a building or whatnot. I've had this exact same syndrome happen over and over. It's fine to toss a couple points into "Read Latin," but for any "adventuring" skill where failure has adverse consequences, you are not going to bother to attempt it unless you have a skill in the 85%+ range.
Does anyone have any good ways to mod the system to mitigate this?
I am not looking for "GM advice." Yes, ideally a GM will remember to apply modifiers to every single skill check, though in "roll vs skill" as opposed to "roll vs difficulty" games they rarely do, or they would make everything into a complex skill check so that the flat roll problem would get normalized. But the system itself doesn't really promote that.
Edit: After all this time, I am still unconvinced. I have run into other people that similarly note that BRP lends itself to swinginess, and though a GM might well be on the ball enough to prevent that all the time, the system sure isn't helping them do it. Still hoping for an answer besides "sweat your GM about it whenever they don't soften failures to your liking."
I was just listening to a Role-Playing Public Radio podcast and they were griping about the same thing. "A professional mountain climber with a 60% climb?!? I'd never even try to get up on that mountain with so low a skill." The default mechanic lends itself to "90% or nothing."