Well, I have a tie between Majesty and Sweetpop. Majesty was a character that appeared in a lot of MLP materials when I a kid, but I could never find her on the rack. I only found out that she's a playset pony when I grew up. Some people may complain that she looks too simple, but I think that's the whole beauty of Majesty. She's just so clean and simple, no pretense or anything. She's simply gorgeous the way she is.
As for Sweetpop, I found her at a flea market many years back, and somehow she gave me a deja vu as if I had her when I was younger. I had quite a lot of ponies as a child but I do not recall owning Sweetpop. Maybe I did? lol Of all the TEs, I'm drawn most to her, and I'm normally biased towards unicorns. I think it's something to do with her blue that's very soothing to look at.