Shemeska
Adventurer
I originally posted this over on the Paizo forums, since I was largely looking for feedback regarding outsiders that have appeared in their Bestiary I, II, TGB, and the two Books of the Damned, but the question is broader really so I'll ask folks here on Enworld as well. 
Allow me to pick your collective brains if you don't mind, but *raises a hand* I like planar monsters. I've created a number of them over the years, and I'd love to snag some feedback from folks as to which extraplanar creatures you've used in your campaigns and in what capacity, and more specifically which planar monsters you really like or really don't like (and why/why not). You get bonus points for talking about any newer outsiders like agathions, azata, proteans, etc.
Humor me if you would (or quasits will come after you. Little known fact: I have a small, trained army of them).
(FWIW this isn't directly related to any current writing projects of mine)

Allow me to pick your collective brains if you don't mind, but *raises a hand* I like planar monsters. I've created a number of them over the years, and I'd love to snag some feedback from folks as to which extraplanar creatures you've used in your campaigns and in what capacity, and more specifically which planar monsters you really like or really don't like (and why/why not). You get bonus points for talking about any newer outsiders like agathions, azata, proteans, etc.
Humor me if you would (or quasits will come after you. Little known fact: I have a small, trained army of them).

(FWIW this isn't directly related to any current writing projects of mine)