I couldn't find a specifically useless thread, but here are a few suggestions:
Spam threads: I've seen a couple where the OP states something that's so freaking ridiculous that it can't *not* be flame bait, and does it in all caps, for good measure. "LIKE, LOL, SKYRIM SUCKS! GO PLAY UR XBOX 750 INSTEAD, ITS SO HOT!!!ONE!"
Something of that persuasion, usually.
AITOO threads: no. You're never the only one with a specific opinion. Shut the fuck up and use the Search bar.
Drunk threads: you're drunk, dude. You don't have any reason or excuse to post when you're drunk. Shut the fuck up and go sober up. Then we'll talk.
Brony defense threads: okay, so the show's fun! Yes, some people will not appreciate it, unfortunately! Grow the Hell up and accept that fact!
Brony-bashing threads: see above, exact same reasoning. Grow up, people have their quirky interests and you can't do a damn thing about it.
Reductionist or Ad Hominem threads: flat-out stating that Anime sucks without providing any argument to back your condemnation up removes any and all credibility you might have. Racist asshats and religious nutjobs and/or intolerants need not apply, as well. This also includes the three billion "People are stupid and I am a misanthrope" threads out there.
Piracy threads: yes, people crack games. Yes, plenty of this very site's excellent peeps have or still do use cracks to this day. No one will ever 'fess up to it, if they aren't morons. Arguing the why or how of it is pointless. Thievery is as old as prostitution, if not older still. Nabbing something without paying for it will always be easier. There is no debate possible on this matter. Get over it.
Oh, and while we're at it? The Escapist is not Demonoid or The Pirate Bay. Idiots who steer piracy threads into sly attempts at mooching for cracks or serials or whatnot are shooting themselves in the foot. Do not bother, you WILL be suspended or banned for doing so.
Meme threads: I don't care about what happens when my Xbox Live avatar gets CQC'ed by Solid Snake! Why do you even want to know?! Why do some people consider threads like these to be fun?!
This is absolutely beyond me.
EternalNothingness' threads: having searched for his profile, I can agree. Oh God, yes. He's The Escapist's runner-up for an equal to That Guy With The Glasses' TheAwesometeer.
Y'know, the one guy who posts absolutely EVERYWHERE every fucking day, but never to add anything substantial?
And yes, this very thread indeed. Decrying the uselessness of threads is in itself useless, as people will always be drawn to useless shit, because it's a mode of personal expression and in posting useless shit, people feel validated or vindicated as individuals. "Hey, lookit me, I posted THAT thread! I sure do hope I get some interesting replies, or else my Ego meter's going to take a drop!"
We're all like this. Each and every one of us, whether we admit it or not. We're navel-gazing monkeys all chirping and screeching to get a cookie in the form of extra replies or badges, and we like it that way.
Charming, isn't it?