Ok now for the actual question:
Bleach - I still love it but the fillers have annoyed me. I do love the Bount Arc and some fillers like that but now the series is going through the 200th episodes and should be reaching the climax (as the Manga is) but instead it's introduced more filler. Frankly at this point, it's not needed or wanted.
Dragonball Z - I grew up on it, so it was one of my early favourites. But during my teen years, I grew sick of things like the screaming for ages to power up, the infamous "five more minutes" in the Freiza Saga and Goku doing something incredibly stupid during the Cell Saga. I recently watched the Buu saga and all of the things that bothered me then still bothered me.
Dragonball on the other hand charmed me, despite hating it at first. GT I detested from start to finish.
Naruto - I have yet to watch any of it. Having been told that it has more filler then Bleach, I don't intend to.
Pokemon - Like alot of people, I was suckered in at first when it began and I did the standard buying the games for the gameboy colour and N64. Then it got dull and repetitive. As soon as they left Kanto, the story was old. I still ocassionally play the game. I am still very proud of catching 147 pokemon on Yellow with no cheating (oh if anyone has a Jinx they would be willing to trade, that would be greatly appreciated

).
Shuffle! - I learnt about its history when a friend told me about it and the fact it is based on an adult game. I began to watch it, expecting 24 episodes of cat-fights. To begin with the girls seemed to have so little character, that they wouldn't even do that. The main character has the choice from five teenage girls, and through out I just was sighing at how stupid he and the story was. However, it got interesting. Backstories were revealed and the 2D female characters had dark histories, strange alter ego or a derailing mental state. Though the ending was back to being incredibly cliche, the couple of episodes that led upto it were well animated, voiced and realistic, which made up for the silliness of it to begin with.
Fullmetal Alchemist - I refused to watched and thought it looked stupid. I watched the first few seconRAB of the first episode and I was hooked. By the end of the week, I had watched all of them, the movie and was onto Brotherhood.
Elfen Lied - As other people have said, the gore and the sympathy for a murderious pysco put me off. I have yet to watch it but I might like it eventually, though I already know alot of what happens from AMVs etc.
One Piece - Have yet to give it the time of day. Just looks too cartoony. Can someone give me a reason to get into it?
Sorry for the rarable.