According to Blizzard, the best all around pet to have is the Wolf. This is because the wolf, has a buff which will buff not just the pet, but the hunter as well. No other pet has this, so for overall dps, the wolf is second to none. According to my powerlevelers, it used to be the cat, which is great for dps and sneak attacks. Blizzard insists, the rest are merely for looks, which is to say, they are all equals... except for the wolf.
I had to transfer an account from one server to the other, and was running around Dalaran as an alliance member. This for me is weird (For the Horde!), but I wanted to see how the other half lives. While I was on however, I decided to check out the macros, that my levelers use when leveling a hunter. For your enjoyment, here they are.
/cast Hunter's Mark(Rank 5) /petattack /cast Disengage /cast Concussive Shot /cast Steady Shot(Rank 4) /cast Kill Command
This one is labeled as "Decursive"
/script Dcr:Println('No spell available')