What an excellent question! XD I just happen to have a definite answer.
I'm just talking about the letters themselves, nothing else.
(BTW I can't believe no one's voted for Q, though! LOL)
Anyway, B and R are absolutely my two favorite letters of the alphabet. There is something about the shape of the letter B that is incredibly pleasing to me. Whenever I have alphabet soup or spaghetti-os or Alpha Bits cereal, I ALWAYS look for the Bs and they make me smile. It's a weird attraction, I don't know, it's hard to explain. Just...B looks so good in so many fonts. Especially when it's thick, and shiny. (I am so weird...) But it's TRUE. Sometimes I see the letter B and it just delights me like no other. Does anyone remember an old educational (bet I just lost everybody, ha) game called "Videosmarts"? I think that's what started my love affair with the letter B...the way the Bs looked in those videos about the alphabet...now when I see ones that remind me of those, I love it! XD
And R takes second place...not sure precisely why...but its shape pleases me too. It makes a good sound and it's just an all-around dang good letter, R. ^_~ It's underappreciated too, I think. I chose it when we had to make a positive/negative space thingie in art class using any letter. My R looked cool. 8]