1) Dragons - I love the idea of more dragons, my main character finally got to go toe-to-toe with one in a scenario last week. It was clearly an adult dragon and it was questionable whether defeating it was within the capabilities of our group or if we should negotiate with it. The tension at the table made it very exciting.
2) Goblins – I personally love Goblins! I don’t think I could really ever get sick of these little heathens.
3) Orcs – More Orcs would be awesome as well. They’re iconic enemies of humanity and also usually a very good challenge.
4) Drow – I’m indifferent on these guys, if more are featured fine, but I won’t be disappointed if they aren’t.
5) Dinosaurs – I could do without dinosaurs at all. They’re cool, but not really what I’m looking for in PFS.
6) Undead – Oh man am I sick of undead, seems like a constant opponent of the Society. I understand why from a writing perspective, there’s only so many things that can be locked down in a tomb for a thousand years and still be there to put up a fight when the Society busts in. As someone earlier mentioned, if you’re going to use them, give them some class levels or something to make them more interesting.
7) Swarms – Eh, maybe a bit overdone, but any resourceful pathfinder can typically find a way to deal with these. I rarely find them an interesting part of the story.
8) Outsiders - Outsiders are very cool and it would be a fun opponent. Just be careful with trying to squeeze them into low level scenarios. They usually have DR of some sort and spell resistance, which can be tough to overcome for a group of young Pathfinders.
9) Humanoid NPCs – Keep them coming, as mentioned there is such a variety here that they don’t feel like repeats. I love scenarios with the Aspis in them, the PFS storyline has done a great job creating an enemy worth hating.