Pets you can never leave with out

[Finduilas]

All my hunters (and that's quite a lot) never leave without:
a) a spirit beast
b) a corehound
once they have reached the appropriate level for PVE. Most times they also have an arcane serpent or hyena with them for the haste buff. I like to have pets that can help my party buffwise.
For PVP I always have a bird of prey in whatever form with me. The disarm is just too good against rogues, warriors,... and also I never leave for pvp without a spirit beast. Because: stampede with glyph = 5 spirit beasts. One click on my spirit heal macro and I have 5 stacks of healing on me. This is just awesome.
The lower once usually run around with whatever I like.

[Aamu]

I can never, ever leave without my wolf Paisley and my warp stalker Radek. It just feels wrong. I've had Paisley since lvl 60 and I've gone through a hell to get him, so I've always kept him with me. Radek was my first warp stalker (I wanted one so badly), and I've never left him in the stables either.

[Clou]

Zujia (Troll) usually has Tribal (Durotar Tiger from waay back), Embers (Terrorpene), and Ethereal (Gondria) with her.

Shuki (another Troll) has Barricade (blue turtle), Chromie (Chromagus), Drifter (Fen strider (Black Stalker)), Ultraviolet (Deth), and sometimes Ethereal migrates over to hang out with her.

My newest Hunter is Naldri - a Dwarf. She still has her original bear (Grumbles) with her - and has recently formed a connection with Lottie (red hyena). Though she's only 58 ATM - she plans to get a warpstalker of some kind later on

[Lupis]

Typically I keep a cat/SB and a serpent with me if I'm going to be doing dungeons/raids. Sometimes a raptor as well for that buff. If I'm just doing dailies, I'll bring a mix of whatever pets I feel need attention, plus one tenacity pet. (Goat, basilisk or turtle.)

[Ghostlytamer]

Yeah I feel yeah I've Always brought Magria and Skoll because they where my FIRST spirit beast and will always be my personal favorites and lets face it Spirit beasts are bosses.

[Mozag]

I usually just have a mix of pets I feel like bringing, and I try to give all of them some airing.

Recently the following pets have been with my hunters more often than not:

Eadgyth - Torch and Spark
Lomelinda - Iris and Willow
Lindorindel - Gabilgathol
Mozag - Mort and Spear
Lazuli - Therese

I am also enamoured of quilen at present, and have given all my hunters at least one, usually two of them. I absolutely love everything about them, and do take them out more than some other pets that perhaps need the outing more.

I also recently culled my hunters, and ended up deleting 13 of them, even max level ones. I had started to feel that the pets they owned began meaning less and less due to the amounts involved and I redistributed many of their most beloved pets to the five hunters that remained. So, some of these I am not yet fully comfortable with and they are still finding their niches with their new owners, which may explain why I am currently using less of my pets than I should. It feels hard to see one of my old Blood Elf's favourite pets on my Dwarf, for example.

[Myrrmi]

I'm a dire-hard BM, and I don't have many non-exotics, there are some, though.

My usual setup for pve grouping is:
- spirit beast - Otso the Arcturis - THE pet for me. And he helps healing <3 (replace with a cat for non-BM)
- worm - for debuff during stampede and for aoe situations - recently swapped my long-time companion Jojo the jormy for Bileworm the amber parasite, just to have some LOLz with him should he get removed/fixed sooner or later (-> replace with a raptor for non-BM)
- quilen - for crit buff and b-ress (-> replace with a wolf for non-BM)

then there are some that I might take for the 2 remaining slots, depending how I feel and where am I going, for stampede buff/debuff menu:
- corehound - Fluffy the Kurken - I don't remember when was the last time I've had to use his hero - you don't really need it in 5-mans nowdays, and in a raid there's always someone with a more convenient version of it anyway; still he's got a nice debuff, and looks nice, too
- silithid - for stamina buff, even though its covered more often than not
- water strider - buffs and waterwalking rock
- serpent - Loki the Spirit of the North - for the buff, although it's often already covered, and for awesome looks
- sporebat - Iluvrogues, because he's The Best Pet (TM). And for his buffs of course

As for others I use occasionally...
- my chimaera only ever sees the outside of her wowkeball in that AQ40 green slime boss room. Never quite figured out how to use her aoe in an effective way.
- my devilsaur gets in party every time I go pvping, his healing debuff rocks. Oh, and for the AQ Twins, too
- Daisy the psychopathic Rhino, coupled with explosive trap glyph, is back in game on every EotS cta. Or at least when I feel I could use some LOLz.
- my shale spider only ever sees the light if I take her with me for some soloing. Very rarely, though, I think I can count her more as retired than not.

[Arthur]

While Skarr will always be my favorite pet I don't always keep him with me. I like to keep them rotated to give them all the attention they deserve.lol.