I suggest expanding the examine tool to reveal a creature's type according to a lore check.
This could give a mechanical use to the lore skill beyond just identifying items that is in line with one of the functions of the knowledge skills that exist in 3.5.
As it is we can only judge a creature's type by observation in the case of the obvious and testing and checking the combat log in the case where it isn't, so a method that allows a character with knowledge to determine creature type via close study would be welcome.
I believe that this can be used to discover (A)MPCs though I would set the DC for their discovery higher than normal monsters, NPCs, and regular PCs so those (A)MPCs that hide among people are less likely to be revealed.
I think it's an interesting idea, though I'll also say using it on AMPC's/MPC's removes a bit of the investigation factor.
Make it a hidden check on a cooldown similar to how Disguise and inspect target works, with non-commital messages such as 'The target
appears to be a humanoid', with an unattainable DC for discerning the true subtype for shapeshifters in their alternate guises; humanoid shape always displays as humanoid subtype, animal form always shows as beast subtype. Do this regardless of whether it's a PC or NPC, so people can't metagame it also. The physical appearance traits brought on by, say, Lycanthropy, aren't sufficient for anyone to conclusively say just by looking at them whether they're a shapeshifter.
Also probably do the same for anything polymorphed, I guess.