Wolf - 5% crit. This buff is up 80% of the time, but if it aint, it's a big dps loss for alot of party members. I always bring my wolf.
Wind Serpent (Or Dragonhawk)- Due to the 8% increased spell damage only being provided by moonkins, warlocks and rogues, this is a must to take with you in 5 mans atleast, because of the huge damage boost (if you are survival) but also for the rest of your group (provided there are some casters)
Serpent (or Raptor) - If there's no warrior or druid tank, you will probably miss out on the -12% armor. Since rogues never use expose armor, and resto/moonkin druids don't use faerie fire. This is also a very big dps increase for physical party members
Cat - The 155 str/agi is a buff provided by many many party members, but if it's NOT there, it's, again, a big DPS loss. I'd say take this with you at all times aswell
Ravager - Last but not least, the 4% increased physical damage taken that this little guy provides, is a pretty decent buff aswell. If you have all of the buffs above covered, bring the ravager.
So in order of buff importance: Wolf > Wind serpent/Dragonhawk > Serpent/Raptor > Cat > Ravager.
I find that in 10 man raids, the Ravager buff is the only one not provided (Frost DK, Combat Rogue and Arms Warrior).
In 25 mans I take whatever pet I want, which is mostly my purple plainstrider
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
I hope this helps picking out a pet DPS-wise, and makes you realize how important our pets can be
![Smile :)](./images/smilies/icon_e_smile.gif)
-Slic