Well, my favorite pony is Twilight, and i'll admit; i have gone through a phase where i had a small crush on her...
But anyway, she DOES represent what i'd like in a partner; she's intelligent, kind, a little bit of a nutjob (as am i), and probably most importantly, she's understanding. She doesn't jump to conclusions like everyone else (well, except in A Canterlot Weeding... and some over things...) and see's the good in people, which is lucky for me.
Plus (this is going to sound stupid) i wouldn't be intimidated or scared if i were in a relationship with her (As most girls/boys do scare me with the possibility of commitment), it's something i could easily do.
Plus on another note, she is pretty attractive for a geek... but that's a different matter...