Millionaire's Special was recently published via Pelgrane, and the profits from the sale of that scenario are going to help Heroes in the Dark. So far it seems to have done really well; when last I heard, sales had topped eighty downloads, but that was a little over two weeks ago so it may well have topped 100 by now. That's very gratifying!
I want to draw your attention to an ability introduced in that scenario: Gambling. People gambled heavily on the old liners. It was one of the main forms of entertainment on what was otherwise a longish trip across the Atlantic. Though the shipping companies did make sure that their floating palaces were well stocked with diversions (including a heated swimming bath and badminton court on the Titanic), the less athletically inclined were more interested in sedate entertainment. Gambling provided that surge of exitement coupled with pecuniary reward. It could be risky. Professional gamblers knew all the tricks, including several that Hoyle never thought of. Unwary travelers could end up much poorer after an otherwise enjoyable cruise.
The issue with gambling is, while it's appropriate to the situation and the era it doesn't lend itself to the pools system used in Gumshoe. There are a lot of abilities with the same problem. I tend to think of these as Silly Skills; abilities that may be fun or develop character but don't otherwise contribute to the plot. In the old Unspeakable Oath (TUO 10) there's an article by Duke Janus, Quirk Skills, that embraces the Silly concept and extends it to all sorts of potential abilities: Analyze Poetry, Annoy Coworker, Perform Tricks with String, and so on. Any Keeper can see the potential here for a roleplay moment, one that could be entertaining in the right circumstances. Entire scenes could be based around a Silly Skill. The old James Bond RPG played much the same trick. There was an extensive shot-by-shot golf game written into Goldfinger, for one, and while that was certainly appropriate for that senario it would hardly be worth inventing a whole new golfing mechanic for a skill only used once.
More often than not, Silly Skills have no real use. They may facilitate roleplay, but they don't advance a scene nor do they achieve a result that has any significant impact on the ongoing plot. Gambling is an appropriate skill for a Titanic theme scenario, and there are plenty of other potential uses for it. Something set in the California Gold Rush or modern day Macau will also have Gambling built in. However most other scenarios won't showcase a gambling opportunity. The same could be said of many other potentially useful abilities. Sports is probably the most obvious Silly Skill; while a character might enjoy playing out a rousing game of tennis or dominating the football match, the player may not appreciate having to spend out of his Athletics pool in order to shine on the playing field.
It's a scarcity problem. There are only so many points to go around during character creation. No player wants to cripple themselves right out of the gate with an ability that sees no use. They also won't want to spend in-game from pools that might otherwise be handy, like spending Athletics on football matches only to find that later in the scenario a well-judged jump from rooftop to rooftop gets more complicated now Athletics pools have been depleted.
Moreover in games like Trail or Call of Cthulhu there aren't many ways to gain more points as the game progresses. Even in RPGs with more significant point gains, like Dungeons and Dragons, players tend not to spend points in skills that don't directly benefit them in some way. I've yet to see a D&D player spend points on, say, Crafting skills who weren't intending to make magic items somewhere down the line. Similarly I'd bet that not many Trail players pick Astronomy as one of their starting abilities, unless they happen to know that their Keeper has a thing for astronomy-themed scenarios. It's not that Astronomy has no use, but that it gets used only rarely, and points sunk in an ability that only sees play once every three or four sessions are all but wasted.
On the other hand, picking at least one Interpersonal Ability (like Reassurance) is a no-brainer. It doesn't matter what the scenario is; so long as it's set somewhere in the real world, chances are pretty good that Reassurance will come in handy at some point. Similarly Evidence Collection is also an easy pick, for much the same reason. It fulfils much the same plot function as Spot Hidden in Call of Cthulhu, and there isn't a Call scenario written that a Spot check won't help solve.
When Janus wrote Quirk Skills his proposed solution to the scarcity problem was simple: don't make the player spend points on Quirks. Instead, let them roll a percentile to randomly determine their level of starting skill, and let things progress from there. While this works for Call, it doesn't help Trail, as Trail doesn't have a random element built into its abilities system. In theory the Keeper could create one, say by making all Silly Skills General Abilities and rolling a d10 (or whatever) to determine starting ability. This doesn't sound very satisfactory, as it eliminates any possibility of character depth. Someone who designs a sporty type with Athletics pool 8+ might only get a 1 on the d10 for Football Ability, while the weedy prof might get a 10 on the same roll.
Some players might enjoy that kind of random element, but I suspect most won't. The player who designs an Athletic type wants to shine athletically, and that isn't achieved by fumbling an easy pass or double-fouling in a tennis match. Similarly the prof might enjoy being a footie champ once or twice, but the player that builds around Library Use and Technical Abilities probably isn't as eager to seek out chances to show off athletically. It's all about player-facing Abilities; the pool should match the players expectations, and that isn't achieved by using a random result.
When faced with situations like these I prefer to base pools for Silly Skills on the character's existing pools in other, relevant General abilities. In Millionaire's Special, I reasoned that Gambling is probably best linked to Sense Trouble. The main rulebook says Sense Trouble allows you to perceive (either with sight or other senses) potential hazards to yourself or others and gambling is all about hazard. Therefore the base pool for Gambling was the character's starting Sense Trouble pool. That way they could spend Gambling points without depleting Sense Trouble, and yet have a base Gambling that reflected their initial character build. I further reasoned that some players cheat, and for those inclined to do so base Gambling could be boosted by adding the average of Athletics and Filch, rounded down. Filch allows nimble fingers . . . to unobtrusively manipulate small objects while Athletics is all about physicality. Nimble fingers and a certain physical dexterity are what card manipulation is all about. I could have added in Conceal as well, since that seems appropriate, but by this stage Gambling was beginning to look crowded. I wanted a General Ability, not an algebra problem. It was simpler to cap it there.
In most cases a Silly Skill won't need to be as complicated. Football can be based directly on Athletics, or horse racing on Riding, without getting any other General abilities involved. Gambling is in some ways a special instance, where the base skill involves several different General abilities. There are bound to be others, but I doubt there are many.
I can forsee situations when this approach won't work. Treating a Silly Skill as a General ability and basing it on other pre-existing General abilities will cover most situations, but perhaps not all of them. Say I wanted to include Trainspotting, or Graffiti Tagging. Those ought to be based on artistic skill or spot hidden ability, but Art and Evidence Collection are not General abilities. It may be more sensible to assume that in situations like those, where there is little chance of a contest and no significant plot function, that anyone with the base abilities Art and Evidence Collection are also good at Transpotting and Graffiti. Therefore any attempt to spot trains or tag a building automatically succeed. So long as there isn't the prospect of a contest, automatic success on non-plot skill checks is reasonable. It's the contest that makes the difference here; if a Silly Skill can't be based on a General ability but does result in a contest, I would have to seriously rethink the problem.
Still, for the moment at least I recommend Silly Skills as a means of solving problems that other Abilities won't fix. There will be times when a chess game or a badminton match are of all-consuming importance to a player, but makes no difference to the overall plot. When other Abilities just won't do, Silly Skills are there to help!