Personally I went for 1066 and all thatfor the following reasons;
1. English being the dominant language which was created by the fussion of after the battle.
2. I'm British/English and it's the largest shift for us in the last Milenium
3. So many others on this list can be seen to be derived from Hastings... alhotugh controversial you could,
teniously argue that the Glorious, American and French revolutions all happend becuase of hastings... but its very tenious
I'm also surprised that the printing press is not on the list, but also the telgraph and maybe, probably to early to tell, the internet... they all revolutionised the spread of knowledge...
As for the splitting of the atom, 'heavier than air' fight etc... although these have had a great impact, the 'ripples' or 'butterfiles' are still not pronounced enough yet to be considered with earlier things like Hastings, the French Revolution or even the The Assassination of Franz Ferdinan, after all the 'recent', in terms of a milenium, has had more time to create 'butterfiles' than the atom....
After all the reason why many people chose early POD's in their writing is that you can make up a totally different world from a different Hastings, but less so from any battle in the second Iraq war...