Newbies starting new threads every thirty minutes?
Oh, wait, that wasn't the question. I guess, my biggest pet peave would be photos that are out of focus, under exposed, and blurry because the photographer was told that getting a 50mm 1.8 prime would magically fix their issues. For me, it's just annoying because I went that route, realized the advice was bad, added flash, and can now do everything I wanted to do.
A flash is, by far, the best investment somebody can make, but generally, it's the last thing people choose to purchase. Makes no sense to me. Not sure why people choose to make their own mistakes instead of learning from others'.