Oh cool, time to vent a little.
1. Fate/Stay Night.
What a complete piece of rubbish. One of the absolute worst things I've ever forced myself to watch. Completely filled with plot holes and things that simply make no sense, characters that I couldn't give less of a crap about and just SOOOooooo boring!
Maybe the visual novel makes sense and is entertaining but, frankly my dear, I don't give a damn.
2. Code Geass.
Seriously people? You like this stuff? I have seen so many people going on about how this is such an incredible series, but... why?
An incredibly dislikeable protagonist, incredibly dislikeable supporting characters, an incredibly dislikeable plot, Code Geass really does have it all! It wasn't smart, it wasn't interesting, and it sure as hell wasn't worth the time I put into watching it.
3. Gantz.
Just completely disgusting. Boobs and gore, what more could we need? Apparently nothing. Because that's all Gantz is.
I'd call Gantz everything that is wrong with some manga/anime, but it'll have to share that title with the next item on my hate-list:
4. Highschool of the Dead.
Yes, that's right! Incredibly busty high school kids amidst a zombie apocalypse. I at least understand why so many idiots love this series.
Thing is, without the frankly insulting level of sexualisation, Highschool of the Dead had potential to be pretty good. It's quite a cool premise, and executed by a competent creator, could have been a real winner. But it was seemingly written by a complete pervert, and as a result became some kind of justification for all the criticism anime is often plagued with.
5. Most of the long running Shounen anime.
Don't get me wrong, I'm a huge One Piece fan, and I quite like Naruto and Bleach. But their anime? I find it incredible that anybody bothers with them. So packed full of filler that it'll take you hundreds of hours to watch what you could have got in a tenth of that time by reading the manga.
I know this doesn't quite fit in with the other items on my list, but in my eyes, the Shounen anime that have hundreds of episodes are the most overrated series' around. People. Just read the manga. Seriously. It's better that the anime, and you'll be able to do other things with your life!
Ugh... that's been waiting to come out for a hell of a long time. There are so many more anime that I've seen that should probably be on this list, but I've forgotten about them. Because they sucked. These ones just stuck with me because their sheer awfulness offended me the most.