Is it: Why do we wear underwear?
Or: What does your user name mean?
Or is it something else?
Evolution vs. Creation
Batman vs. _______
Hey! * Batman vs. Creation*.
Batman wins by evolving preparedness. 
Evolutionary Underwear gets my vote.
Or a Predict the next/last… thread.
LOTR seems to come up quite often in CS.
I think GQ might get it for most threads about computer problems.
The British judge gives you 73% for irony
Thank goodness its not a thread about shaved pubic hair. When I first started lurking there seemed to be a lot of threads about somedoper shaving their pubic region.
Been hearing lots of badger badger badger badger mushroom mushroom in MPSIMS lately.
“Ask the …”
“Best (bleh) Lines”
And of course, “I hate/love/wanna-hump-the-writers of [insert eagerly anticipated movie title]”
Metathreads (threads about threads, or threads about themselves)
Marmite vs. Vegemite vs. People with no taste. 
I’d say the “Why is this board so sloooowwwww???” threads have 'em all beat.
Bah. I see a new Prove to me that God exists!! thread every other day in GD. That or Abortion kills babies! / What’s wrong with killing babies?
How about sequential thread titles? There almost always seems to be one going in MPSIMS.
My vote is for spelling pet peeves.
Oh, and there’s no O in recurring.
The one I always seems to see in Cafe Society is some variation of “What’s the best cover song?”
There’s never any original answers. Every good one has been mentioned. Yet they still usually manage to go for more than a page.
Homosexuality.
Sex threads… any of them!
I’m going to have to ask for my money back on my text editor. The spell-checker said reoccurring is just fine.
Ooops, the editor was free
Hmm … reoccur and reoccurrence seem to be just fine here:
Two words.
Simp sons
Lately:
“My theories on the Matrix trilogy”
But I’m going to second the “sequential thread titles” threads.