I did mine on "How much influence did Tony Blair have on US foreign policy", which I thought would be interesting, but then found it quite difficult working with contemporary sources, as I prefer historical analysis, really.
Other than that, like Mao Cap I was alright when I got going and got a half-decent mark. Got a 2:1 for my degree which, considering I'm a p*ssed up tw*t, was good enough for me!
Have a really good idea for a Master thesis if I ever decide I want to do one - comparing the 1815 Treaty of Vienna, and the 1919 Treaty of Versailles. One fine day I will write it....