If you want a free op, I'll do it for any video. If all you want is purely positive stuff, here is a list of things I don't like:
-feminine anime (I just mean art style. even stuff like Elfen Lied kinda pushes it)
-anime with lots of magical powers (this seems to tie into the first one)
-"super cute" anime
-music videos with only action scenes with your favorite song
-death metal/ultra hard rock
-boy band/girl bandish pop music
-non english music in general
I'm not saying that I will automatically hate your video or anything. I've liked a lot of videos that have some of these things, and I'll try and be as objective as possible until I get to the "re-view" and "overall" parts anyway, but you should know that these are things that make sitting through a video difficult for me, as they usually come with other problems.
Finally my grading scale will probably seem a little harsh. 5 is average for me. I'll repeat: getting a 5 on something simply means I think you did average. That said, I'm pretty lenient on the sound and video quality stuff unless they're really messed up.
I try to leave as much feedback as possible. I tend to clam up more if it's something I like, but if I do like something, I'll try and explain why I liked it as well.