I've always been a fan of peophins, the chocolate one and the magma ones being my currents favorites.
Faerie Draiks are pretty awesome...but I totally agree with Mutant Hissis. I've wanted one since I saw them for the first time. Originally I wanted an UC, but the converted ones are growing on me. Other than that...I really like the pets that look like real animals. I think they're pretty clever, honestly - the spotted Lupe which looked like a African Wild Dog, the Mutant Lenny which is a vulture, the Maraquan Lupe looks like a sealion...and on. :3 Every time they release a new pet that looks like a real animal I get excited.
I personally love maraquan pets. Most of them i think are done well, i dislike some of the newer ones, like the kacheek & poogle. My favorites are the kacheek, tonu, gelert, draik, krawk and a few others. I also like the new color water, it is done very well.
I personally love the Stealth Blumaroos. When mine got zapped into that a few months ago, I just about died. Hah! (unfortunately, being a lab pet, it's no longer one now )