I feel like a lot of the "recommendations" on this list are by people who feel burned by the heavy hype of a series.
Attack on Titan is good, Evangelion is good. I like them both a lot. They get hyped as life-changing incredible experiences, and maybe for some people they are, but just because you don't see them as that doesn't mean they're bad or not worth watching. They both have their issues (pacing problems, Titan has too many characters, Evangelion's characters can be pretty grating at times), but just because some fanboys on the internet crow about them endlessly doesn't mean you'll look cool and edgy for hating them.
As for my own don't watch list, I'll say:
Code Geass: Mentioned repeatedly on this threat, but I really need to stress that you shouldn't watch it. I did and regret it every day. Things start out promising enough, and there are some memorable moments, but Lelouch is an atrocious protagonist, his friends and allies are either callous douchebags or brainless pawns, and his enemies... holy shit, if Suzaku isn't the worst characters in anime, then he has to be top ten. It brims with xenophobia, depicting Americans as mindless imperialist assholes, Europeans as haughty aristocrats, Arabs as greedy and sleazy sheiks, Chinese as backwards and corrupt eunuchs... if you aren't from Japan, Code Geass says, then you're some kind of disgusting garbage. The show's few redeeming qualities are the mech fights and a few of Lelouch's early plans are fun, but just as you get comfortable, the anime proves itself to be utterly incompetently written.
Oh, and Kallen's great. She deserves to be in a better anime.
Tenchi Muyo GXP: This was on Toonami a while ago, and I decided to give it a chance. I didn't expect to like it, but I thought it might surprise me. I haven't watched the main Tenchi Muyo series, it's apparently pretty good, but GXP is a mess of atrocious animation (there's a loop of our forgettable lead on a bicycle that is used like five times in the first episode), terrible characters, an uninteresting and generic plot, and is just plain boring. Don't watch unless you're a die-hard Tenchi fan, and even then I still can't recommend it.
Casshern Sins: A remake of a 70's anime, Casshern roams a boring wasteland fighting boring robots in a boring way. Every conceivably interesting character dies immediately after they're introduced. The "mystery" that drives the plot is one-note and completely easy to figure out. Watch Fist of the North Star instead, because at least that series has heart and likability. Casshern Sins is just a shameless, mercenary cash-grab on a potentially lucrative franchise.