I'm going to just stick to pets I actually have. And I'll post my favorites of older lines and the newer lines when it applies.
Eld Favs
Ancients:
Basilisks:
Chillawings:
Cuttlefish:
Dhol'kai:
Dire Wolves:
Elkrin:
Foo Dogs:
Glasswork Dragons:
Griffins:
Humming Bumbles:
Jackalopes:
Ligers:
Otterlings:
Phoenix:
Prong Foxes:
Rune Dragons:
(I can't even! This might be one of my favorite pets ever XD)
Rune Drakes:
Sea Servals:
Sleipnir: