/pet as you were -- Makes pet forget all other commands and clears their aggro list.

/pet attack -- Pet will attack targetted creature

/pet kill -- Same as pet attack.

/pet back off -- Tells pet to quit attacking target. Note that if a monster attacks either you or the pet, the pet will start attacking again.

/pet follow me -- Pet will start following you (cancels any other guard commands)

/pet get lost - pet suicides

/pet guard here -- Makes your pet stand in one one location and attack any NPC that comes near, including guards. He will return to his original location after the fight.

/pet guard me -- Pet follows you around and attacks any NPC that comes near you.

/pet who leader -- Pet says "XXX is my leader." Used pretty much only by Enchanters and others who can charm critters.

/pet report health - Your pet will tell you what percentage of HP it has left. Useful, since you don't have to target your pet to find out how close to death it is.

/pet sit down -- Causes pet to sit in one place and rest much like you would sitting down

/pet stand up -- If your pet is sitting, he will stand up. Personally, I just use /pet follow instead of this.

/pet target -- Targets your pet. (also works if you hit F1 twice)

/pet taunt -- Your pet will taunt its targets.

/pet no taunt -- Your pet will not taunt its targets.