I think it might be best to have some general, broad categories of types of dumb shit as well as a few examples of each. For instance, politically captured articles full of dumb shit and lies, i.e. GamerGate/Kiwi Farms/etc., usually patrolled by naked propaganda. A lot of these involve portrayals of absolutely idiot lolcows by completely uncritically repeating outrageous lies told by the cows themselves that ended up in fake news, i.e. "reliable sources."
Then there are things like autistic talk page slapfights, which can be pretty funny, edit wars, ArbCom cases, and things like that. Ryulong's autism tantrums would fall into this category.
Then there are just plain stupid articles, either because "why is there an article" or because the actual contents are stupid.
The last example would be some of the hoaxes and frauds perpetrated, i.e. like that idiot autist who created thousands of "Scottish" wikipedia articles even though it was by an American who didn't even speak the language and just talked like Scrooge McDuck.