well, for starters, i still need the silithid hatchling, which only come out during sandstorms. so i keep an alt parked in gadgetzan and i periodically hop over to her to check the weather. so far, no luck, or, as my grandfather used to say every morning after moving the family to southern california in the 1950s, "well, another goddam beautiful day."
another reason i can often be found in tanaris is that it is the perfect spot to grind on those "raise x pets to level 10" achievements. the locals are all level 13 which means that (a) they still operate in pairs instead of triplets, and (b) it's almost impossible for them to one-shot a level 1 pet. so i typically run with one baby out front, and at least one 25 for back-up. send the baby in first, let him take a single hit, then swap in big sister to crush the locals. if you only do one swap during the fight (ie, don't use your third pet at all), you can go from level 1 to level 6 with just five fights. getting the next four levels takes a little longer, but with a stable master in gadget for quick repairs and lots of pets not far from the city, it still doesn't take that long. just watch out for the desert spiders - their sticky web ability can snare a baby and keep you from swapping it out before it dies. best to send a level 25 in first, and then swap the baby in for a round against the second local (assuming it isn't a spider also).
so far i've used this system to finish out no favorites and rookie pet group, and i've nearly finished rookie pet crew (just 3 or 4 more to go). then comes the seventy-five pets for rookie pet mob - i suspect i may cheat some on this and trap a bunch of level 9 prairie dogs over in the south barrens for part of this...
anywho, once you've gotten a pet to level 10, if you want to continue to level him you can actually take him to pandaria. again, the odds of getting one-shot at that point are pretty low, and the xp you get for surviving is truly bodacious.