It's the quest you get from Aodhan to go and get "The Bomb Tossin' Pro" title for the secondary weapon prof book.
I already got the title and everything, the requirement is blotted out in the quests page, and I see the yellow question mark box above the quest when I talk to Aodhan, but he just tells me to go and bomb more, like he does when the quest isn't finished.
:what:
*Edit. Wow really. It worked when I took it off the quests sidebar.