To be totally honest, I don't think I have ever used Fatty's ability. I have always just used him for his defensive stats which are actually pretty good, especially for a low threat hobbit(koff koff Bilbo). I'm kinda sad about this because I always liked Fatty as a character and it's a real bummer that Folco Boffin is amazing while Fatty's ability is awful. I hope they come out with a new version of Fatty eventually or errata this one to improve it(or both!).
Fatty Bolger
Hobbit.
Action: Exhaust Fatty Bolger to choose an enemy in the staging area and raise your threat by that enemy's . Until the end of the phase, that enemy does not contribute its . (Limit once per round.)
The Black Riders #5. Spirit.

Everyone says that Fatty is a horrible hero, and blah blah blah. But I disagree. Now, don't get me wrong. I'm not saying that he's the best hero in the game or anything like that, but I like him. His ability isn't great but it's still pretty good if you're in a tight spot and need progress on a quest card or something like that. Just add threat reduction or Loragorn and now you can use his ability a little bit more often. Also, he has 2 which isn't a lot, but for a hobbit it's great. Give him DĂșnedain Warning or Hobbit Cloak, Ring Mail, Staff of Lebethron, etc. and he can now take Nazgul attacks in stride.
I would just like to say that Fatty Bolger as a character is getting a major upgrade, thanks to A Long Extended Party. He deserves it.