Honourable Mention: Sharpeye Stella, Vinosh (in any form), Samurai Girl Sakurako, White Tiger Lily, and a few others.
I pretty much agree with everyone else on this one. But add these:
I think the Star Light concept is interesting, because it's the first pet to be made out of many (I think?) but I honestly cannot stand how those girls look. I wonder why they never made a Matrimony Set including both the bride and groom pet?
I'd be in trouble if I could afford all my favorite pets. Especially Singha the Redeemed... makes me lol everytime I see that animation. XD
Edit: Looking through the post, I think Yukata Dorothy just made the list of my favorites. o.o