Pet Tanking Talent Choices

20 Talent Points Not 16 Talent Points
First off, let me say that you don't need to be BM to have a tanking pet. But if you're planning on solo'ng anything difficult, or planning on tanking a heroic or raid, you need to have your hunter with BM talents. I'll cover those in another post. Suffice it to say, your pet will have 20 talent points to allocate, not 16.

Tenacity FTW
Tenacity pets are the tank pets. You don't use a Ferocity or Cunning. Tenacity pets have talents that allow them to, if used correctly, tank mobs. Don't expect to use a non-Tenacity pet as a tank. It will only get you so far.

Re-Talenting in the Field
If you're a dual talented 51-pt BM and some non-51st-point-BM talent build, it's easy to re-talent a pet on the fly without visiting a pet trainer. Just go BM and spec your pet with its four extra talent points. Then flip to your non-BM talent tree. Re-summon the pet. It will have no talents. Flip back to BM, talent the pet up, and suck down some mana.

If you aren't dual spec'd with this as an option, maintain tank pets for different situations. You can flip them in the field every 30 minutes.

Tanks would kill for the ability to re-talent on the fly. What they can do now is swap gear. And maybe the crazy tank is dual spec'd in two tank talent allocations. I doubt anyone is that crazy. But then again, there are hunters who think they can have pets tank.

Abilities (Talents) You Can't Allocate
Pets come with at least one special ability. Generally speaking you want a Turtle as your tank for it's shield ability. A Gorilla with its interrupt may be a good situational use pet tank. Gorilladins were the first favored tanks because they and only they had thunderstomp. But now they only have their interrupt. Worms have something approximating a sunder. Beloved bears have swipe, a second multi-target threat builder.

In my opinion, turtles are the best all-around heavy-tanking choice because of their shield. All the others are fun choices and still viable -- especially for certain situations.

Pet Talent Builds for the Job

• Soaker Raid Build: The pet doesn't need to compete on threat vs anything except proximity healing. Optimize for stamina and armor. Thunderstomp is there for a little extra threat generation. The same with Guard Dog. If you think you can even skimp a little on those go then steal one point and put it into an armor talent.

• Solo Tank Build: The pet doesn't need to compete with threat because you're the only threat competition. And you can feign death, right? This is optimized for health regen and avoiding damage. It's good for doing AoE packs, minor bosses, or solo'ng old content.

• Five Man Heroic Build: The pet needs a lot of bells and whistles. This has a good mix of bail-outs for group members and it generates threat pretty well.

Situational Supplemental Talents

• The Lionhearted talent is completely situational. If you don't have a priest or shaman it can help. However, 30% less stun or fear is still 70% stun and fear.

• Great Resistance is also situational. If you know an attack will be almost entirely fire, frost, nature or shadow, then flip three points from armor (aka physical or white damage resistance) into Great Resistance. It can only help. But you better know that white damage is almost non-existent.

• The Five Man Heroic Build does not have Intervene. If you want to use Intervene you'll want a macro for it. /targetpettarget ; /cast Intervene. I find it cumbersome. Some people recommend that you consistently cast it every CD on your healer. That sounds crazy to me and a waste of 20 focus. I have too many buttons on my bars already so I simply avoid it by trying to stack more threat at the right time on the right mobs.

If it helps, you should print out the three pet talent trees filled out. Keep them near your computer. Practice flipping them in-game and re-talenting quickly. In a group you don't want to be taking the same time it would be to hearth back to a major city and re-talent.

EDITED TO ADD: Re-talenting in the field is no longer possible!