Agro was appreciated, but I can't say I was moved by its story. People talk about how Epona's "just a horse," but Agro struck me like that even more. Epona moves better, she has a song required to tame her, other characters interact with her, and you watch her grow. Throw in having several other games, and Agro looks outclassed.
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http://img812.imageshack.us/img812/3492/eponaharr.jpg
Nominate E P O N A.