Qarn HM, over 50 runs, I stopped counting.

However my worst luck was for an item drop in a MMO was in FFXI, farming for the Ochiudo's Kote. It was an item drop from a Notorious Monster with a 50min-6hour spawn window, but it had a little under 50% chance to drop the item, so you would think it would be easy to get...it took me over 150 attempts to get the item before I just gave up, that is right I never even got the item. I think I spent like 2 weeks camping pretty much just that NM...