This is one thing that doesn't bother me. At least in the Japanese version of most series, the boys actually sound the age that they're supposed to. In other words, it's realistic. This is my main gripe with dubs when it comes to boys speaking. They usually sound too old for their age or for their size. Yugi comes to mind for me. I've heard his dub voice, and he sounds way older than he should be. Of course this isn't always the case, even for originals, but as I mentioned, at least it's realistic that they use women who sound like pre-adolescent boys for like 12 year old male characters as opposed to having an adult male voicing them.

Beyblade is another series I didn't care much for voice wise. Our main five, Takao, Kon Rei, Max, Kai, and Kyouju sound realistic for the original because they're all 12 year old boys when it starts, yet, for the dub, Takao (Tyson), Kon Rei (Ray), and Kai all sound like adult males. Way too old given their ages.

Max and Kyoujuu (Kenny), however, both sound the ages that they're supposed to because both were voiced by kids and as the characters aged, so did the boys doing their voices, so they sounded more natural as the seasons went on.

Three way tie between Dubs, Filler, and those terrible endings that resolve nothing. The worst dub I've heard so far is Rurouni Kenshin (he sounds like he's either a young girl or a boy in the middle of puberty), worst filler of course is Naruto (I mean they actually had to start a new series just to move away from it!!), and I'll agree with everyone else and bash Inuyasha for its horrible ending (though Flame of Recca's also irritated me quite a bit, and Histories Strongest Disciple Kenichi stopped right before the best part). These three things are why I mostly just read manga now.

i hate when the anime ends before the actual manga plotline does, so they have to make up a "new" ending so they can end the anime. half the time it makes no sense and they reslove things in a stupid way.

I'll say it but you'll hate me for it.

I can't stand MECHA.

*runs away*

You know what just popped into ma' noggin? An anime revolving around the life of a mecha technician.

Seriously, how in the world do those things work? Besides, gotta' give props to the lil' guys every now and again.

When it ends in general.... I hate it when really good series ends. Like Trigun or Outlaw Star, or Cowboy Bebop. I hated it when those ended.

you have a fair point. people don't just find mecha while digging undergound (gurren lol) someone had to build them at some point. where do they get all that metal from and what factory is big enough to mold metal pieces of that scale?

Filler
Cliches
English Voice Acting

those are some of the most annoying things.

Whenever a cool supporting character has been reduced to standing back and stating the obvious!! Like what happened to Tuxedo Kamen-sama! He started out cool, then they had him show up, state the obvious, then leave! WHAT THE HECK IS THAT!!!???