I'm not sure yet myself what im doing mine on but I would suggest stay well clear of ww2 / rising stuff because they're done so much it's more difficult to stand out and do well. A local project tends to score well for example history of a local gaa club because the examiner won't even know about the club most likely so you won't be marked down on historical accuracy. The Bermuda triangle has some interesting plane accidents that I was thinking about. Google flight 19 its very interesting and there's loads on it. There were some utterly mad dictators in the middle east and asia down through the years any of those would be very good as well.
Hope this helped and may the odds be ever in your favour!