The Snoop archetype of the Rogue class as detailed in Ultimate Intrigue has an Inspiration class feature that is in most particulars identical with the Investigator's feature of the same name. One difference is that the Snnop's Inspiration is described as being usable with skill checks but not with attack rolls or saving throws.
However, the Investigator's version of Inspiration can also be used with ability checks. So does the Snoop get to use Inspiration with ability checks or not? On the one hand, the text for the Snoop's Inspiration says that it can be used only with skill checks, but on the other hand, the text also provides a list of checks that the Snoop's Inspiration cannot be used for -- and ability checks are in neither list.
I think by RAW ability checks are excluded, but the exact wording seems to imply that a direct statement one way or the other was inadvertently left out.