Another list. made from a different angle.
Xu-Fu, aka Aranesh, who keeps the most comprehensive and up to date strats on [url]http://wow-petguide.com[/url], kindly makes available the list of pets used for the preferred strat in each range of battles, and how many times each pet is used.
I pasted all of these lists except one into a spreadsheet and added them up. I excluded the Family Familiar achievement, since that takes us to some strange places, and adds a lot of one-off pets to the list. Whet we should have here is a general sense of the usefulness of each pet to the beginning battler facing tamers and World Quests. The total number of uses of the pet is on the left.
17 Chrominius
13 Anubisath Idol
13 Teroclaw Hatchling
12 Iron Starlette
10 Ikky
10 Mechanical Pandaren Dragonling
8 Clockwork Gnome
8 Nexus Whelpling
8 Unborn Val'kyr
8 Zandalari Anklerender
7 Darkmoon Tonk
7 Emerald Proto-Whelp
6 Darkmoon Zeppelin
6 Emperor Crab
5 Any Moth
5 Any Snail
5 Scourged Whelpling
5 Stitched Pup
4 Eternal Strider
4 Nether Faerie Dragon
3 Sprite Darter Hatchling
3 Zandalari Kneebiter
2 Any Fox
2 Any Rabbit
2 Effervescent Glowfly
2 Fluxfire Feline
2 Menagerie Custodian
2 Red Cricket
2 Shimmershell Snail
2 Silkbead Snail
2 Sunreaver Micro-Sentry
2 Swamp Croaker
2 Tranquil Mechanical Yeti
2 Voodoo Figurine
1 Any Roach
1 Cockroach
1 Cogblade Raptor
1 Corefire Imp
1 Crow
1 Dark Phoenix Hatchling
1 Draenei Micro Defender
1 Elfin Rabbit
1 Fel Flame
1 Flayer Youngling
1 Fossilized Hatchling
1 Ghastly Kid
1 Ghostly Skull
1 Infinite Whelpling
1 Kun-Lai Runt
1 Lesser Voidcaller
1 Lil' Bling
1 Lil' Tarecgosa
1 Mei Li Sparkler
1 Mini Mindslayer
1 Mr. Bigglesworth
1 Mr. Wiggles
1 Mud Jumper
1 Pandaren Water Spirit
1 Rabbit
1 Sandy Petrel
1 Sea Gull
1 Son of Sethe
1 Wild Jade Hatchling
1 Wildhammer Gryphon Hatchling
Some comments:
I'm a little surprised that [pet]Bone Serpent[/pet] and [pet]Blighted Squirrel[/pet] aren't in there anywhere. Maybe I should popularise some strats for them.
Bone Serpent is infamous in PvP, but can plug a lot of holes in PvE teams as well. OTOH, when you are trying to make a repeatable strat, you really would prefer to avoid introducing a 10% miss chance with Darkness. And Ikky's Black Claw/Flock covers the same ground as the Squirrel's Woodchipper/Stampede combo.
I'm also a little surprised to see [pet]Chrominius[/pet] still so dominant, now that his partner in crime, the [pet]Pandaren Water Spirit[/pet], is reduced to a shadow of its former self. But that Howl -> Surge of Power combo still nukes just fine.
Breeds. If you say to me "Hey, I'm off to get one of these pets. Which breed should I pick up?" my first answers would be:
"Any Moth" - I love [pet]Yellow Moth[/pet] P/P, [pet]White Moth[/pet] H/H, and [pet]Gilded Moth[/pet] H/P
"Any Rabbit" - any S/S that has 357 speed at level 25, like [pet]Spring Rabbit[/pet] S/S or [pet]Alpine Hare[/pet] S/S
"Any Snail" - my personal go-to is [pet]Shimmershell Snail[/pet] H/P, but they all work fine.
[pet]Emperor Crab[/pet] P/P
[pet]Emerald Proto-Whelp[/pet] P/P
[pet]Iron Starlette[/pet] - I want to say H/H, and I want to say P/P, and I want to say P/S. I don't know which to pick. They all work pretty much the same way.
[pet]Kun-Lai Runt[/pet] P/P or P/B
[pet]Nether Faerie Dragon[/pet] S/S, but pick up a P/P as well while you're there.
[pet]Scourged Whelpling[/pet] H/H
[pet]Unborn Val'kyr[/pet] - both breeds are good. I
slightly prefer H/H, but either will do.
[pet]Nexus Whelpling[/pet] P/P
Zandalaris - go for Power. P/P or P/B.