as a gm what characters irk you.

[Myrrhibis]

I try to keep any given group within the same range of destructive potential, give or take 100 MDC. Otherwise, I limit players not characters. I'll ask them to come up with a reason why their character is present and participating in the adventure rather than tell them they can't have a specific class. And, if they're not able to come up with a compelling reason for their coalition intelligence specialist (or other equally unlikely class) to be paling around with an elite group of alien mystics (or other equally strange cohort of player characters) on a search for their magical messiah (or other equally odd adventure), I'll usually suggest something.

This is most common approach by myself & the other usual GM.

We have experienced PB players, so they know what's out there. Generally, explain your char concept & it'll usually be approved - with warning about anti-DBee/mage bias, or that you have inherent pro-con due to familial contacts. Equipment is slightly limited - again, based on char concept.

We have had games that are restricted to a half-dozen or less books, folks adapt well to those.

[Lukterran]

In regard to PFRPG

I allow all base classes and races that are in the Main Book. Almost all PF monster races are allowed as player characters. Except for a few exceptions i.e., most supernatural monsters including undead and faeries; Ki-Lin, Lizard Mage, Sphinx, Dragons etc...(monsters with animal intelligences are also not be allowed as PCs)

All classes within the core books are allowed
No Rifts or alternate dimensional classes or characters
No Rifter anything is allowed

I could careless about the character race or class that is played. What I really want to see is if that player is creating a character with depth and personality that is role-played accurately.

I will nerf something that unbalances the level of play for all players involved. So if one player continually steals the thunder from everyone else (Not because he is clever or a better player) but because he has "unearned" advantage over the others than I will limited it before it ever gets into a game.