I could never get into the mech/giant robot type anime, so things like Gundam I never really liked. Also, when Kekkaishi was airing on Adult Swin I tried getting into it but I just couldn't. I love you Vic Mignogna but not even you could keep me watching that show.
I was a fan of Naruto for a while (mainly because of characters like Kakashi, Shikamaru, Neji, Kiba, and Rock Lee. I hated Naruto, Sasuke, and Sakura.) but I lost interest when the series decided to turn into "Sasuke: Featuring Naruto"
Also Bleach. I tried getting into it but there's just too many characters for me to try to keep up with at this point.