I think all the characters had their moments of annoyance, but Alison takes the cake for me. She acts like she has a stick up her bum and is so self-rightious it's insane. Season 4 changed my opinion on Jane, she went from sweet to manipulative and annoying, and even going back and watching the first 3 seasons, Jane is really irritating, and I never noticed it. Sydney can be irritating, but most of the time she's just fun. I think sometimes Jake can be so annoying with his obvious pride and sometimes self-rightious behaviour, although he is not as bad as Alison. Oh, and I forgot, Brooke is absolutely irritating but I like Kristin Davis, so I could actually deal with her, and she wasn't in the series for very long, so it wasn't a hassle putting up with her as it was for others who were in the series for longer.