In terms of fluff and description, how would you describe a ranger with an odd choice of favored enemy?
A ranger with favored enemy animal is what most people think when they hear "ranger." Favored enemy: humanoid is for bounty hunters and serial killers. Favored enemy: magical beast is anyone from the video game Monster Hunter. Favored enemy: undead is a lot like an Inquisitor. All of these are pretty easy to come up with a character concept for (assuming you're using your class as the base to work on).
But what about a ranger with favored enemy:ooze? What does that look like? Or favored enemy: aberration? Construct? Vermin? Plant? What doe these guys look like?
Favored enemy: ooze = Cleanup specialist.
Favored enemy/Aberrations = Defender of Nature, Slayer of the Eldritch Horrors, etc. Aberrants are the ANTITHESIS of nature.
FE: Vermin = Bug Hunters, or Exterminator, as above.
FE: Plants = Lumberman, Firesetter, or Reaper of the Green. Note in places with hostile plant life, this is a highly believable FE.
Harder to justify FE: Lawful/Chaotic outsiders, since they just aren't occured as recurring foes too often, unlike Evil ones, which are all over the place.
Most of the odd FE's would reflect specialists in a particular field, or those with an overwhelming abundance of a particular foe. ANimals would be your average hunter. Magic Beasts would indeed be a trophy hunter. Any humanoid would reflect hostile relations with a large number of them in the immediate area. Dragons is something for the heroic. Undead in someplace like Ustalav is totally believable as a primary.
An ooze specialist probably cleans up after magical accidents. Given the breeding rate of insects, a Vermin hunter is likely never out of work, and probably does a lot of sewer work. In any areas with a strong fey prescence or elves, there's going to be a subset of rangers good at taking out animate plants. You only want to be on the receiving end of a treant and friends ONCE.
==Aelryinth
Favored enemy constructs = Deconstructionist
The most common FE's are probably Human, Evil Outsiders, Undead, with Dragons, Aberrations, and Giants vying for tertiary importance. There are AP's where Monstrous Humanoids and Elves get more light, but that just means Humans are less featured and you can swap in for them.
Basically, any adventuring ranger had best get undead and evil outsiders, and everything else is optional. Human is a great fallback and can be swapped out for whatever the main enemy of the module is. The rest are corner cases that appear fairly frequently. FE: Constructs = an adamantine sword.
==Aelryinth
Rangers work best within the confines of the campaign they play. Ranger A works well in Game C but not so much in Game D, based on the the environment. Which is where you should build a ranger from, I think.
To maybe answer the original question, the first four favored enemy choices have a dwarven face.
Though fey, plant, elemental lean towards an elf ranger.
And freelance rangers on Golarion are wise to choose humanoid (human) as a favored enemy, as there are many more of them than any other subtype in Golarion.
Favored Enemy: Animal = Man vs Food.