I'd like to see the filer options on this site brought more in line with what Blizzard has on the Armory.
Specifically, all the pets that can be fished up (including the crocolisks) are listed under Professions on the Armory while they're all under Drops here. They also have an option for World Events that collects all the various pets that can be obtained during the various holidays. Currently these are pretty spread out here, including all the Children's Week pets (under Quest), various pets dropped by holiday bosses (Drops, obviously), and a few pets that can be purchased with the special holiday currencies (under Vendor).
I came across this while trying to match my collection on the Armory with my collection here. I began by using the same filters on both sites to see where numbers didn't match up, but nothing matched up since there are so many that are listed differently.
Currently, there are a lot of pets on the Armory that seem to be filtered incorrectly (for example, the Thundering Serpent Hatchling incorrectly comes up as a battle pet) or are missing entirely (Crimson Moth and Wharf Rat for example), so it's probably asking too much to see the same numbers in both places using the same filters. However, I think that having the filters here match the ones on the Armory would make a lot of sense.