One name: Rose Garden.
Does treasure and tribulations count? Must've done that BCNM 100 times, I've only ever picked the right chest 2 times. I guess it's sort of comparable to a drop rate.
Haven't spent a whole lot of time really camping anything since I returned after a years abscence... But prior to my break, you can just put in whatever NM you want, and that's my annoying drop rate.
I've spent about half my playtime over all my characters, camping a drop.. NOTHING EVER wants to drop for me and it pisses me the hell off... Every dynamis I've ever went to, every single other drop will drop (often more then once, yes even AF) but what I want NEVER drops.. Nyzule runs adhere to the same behavior. What adds insult to injury is the fact that pretty much any NM I just happen to come across and kill, drops it's most sought after and rare drop... Only problem is I most often only run into NM's that drop items no one really wants (some of the new synthesis materials and the new NM's that drop them come to mind, like radiant velvet) or they drop things that are now obsolete either due to a bigger better replacement, or have fallen in price so much it's just not even really worth worrying about.. Rabbit Charm for instance used to be worth millions, now it's worth a couple hundred K, which anyone with a 75 job can farm the gil for in no time.
What drop rate annoys me? All of them...