Well tough choice, but i'm gonna have to go with either brian or stewie, because they are actually intelligent. While i love the stupid humor their humor tends to make me laugh more because its a pause from peter's stupidity.
I thought twice about it, and now I realize that it is Brian. I like the actor's voice, and how he is always cutting Stewie down, and sometimes just hanging out with him.
I like Brian, and Peter. One episode that got me laughing for 5 minutes... literally! *Brian walks in* What are you doing? Peter: *talks casually* Crack... Brian: What the Beep! *brian walks out* *Brian walks back in* *peter rocking back and forth, holding a couch pillow* Peter: Gava mant gone took ma beby!