Interesting topic! But maybe you could explain more by how those tropes/cliches/stereotypes turn you off from certain manga? Like, with moe, to me moe is a really broad term that could mean anything. Yes, there are "moe" series, but there are also manga/anime where the moe gets hyped up despite the plot being different. People also describe certain art styles to be moe. A specific character could be drawn moe and have their sole purpose be moe too. I just wanna know your reasoning. :P
As for me:
-Confusing/overcomplicated pilot chapters. If I can't follow along in the first chapter, I get frustrated. I understand a lot of mangaka want their story to start out with a bang, but I'd rather the plot start simply, and then build up on complexity.
-horror & gore Like Asarii, I really cannot stomach horror or gore. Yes, I've read horror manga before, but I'm more used to mainstream gore, like Hellsing and Gantz. But true horror manga/anime, I'd never be able to handle it. I just wouldn't sleep at night.
-sports manga Like Doraku, I really have no desire to pick up sports manga. I understand their popularity, but I think it would take a lot more investment. But its not because I don't like sports, its because of the next dealbreaker...
-lack of prominent female characters. Truth is, the reason sports manga tend to be dealbreakers for me is because the ratio of male to female characters get seriously out of whack. Sure, its nice to look at well-drawn men fighting and breaking into sweat, but it gets boring for me after a while. And this extends to beyond sports manga. If I look at a manga's promotional images, and there's a lot of Men Doing Things with maybe one female side character, it just doesn't cut it for me. Its frustrating.
-love triangles. Love triangles aren't quite the dealbreaker for me, but they do lower my opinion of a manga. And it seems to be the bread-and-butter for a lot of manga. They'd have to be executed extremely subtley and well-done in order for me to tolerate them, otherwise I cannot stand them at all. The indecisiveness is often terribly done and I end up feeling the author assumes I'm an idiot for not knowing who the main guy (or girl) will ultimately end up with.