1. Hastings - 1066
2. Stalingrad - 1942/43
3. Leipzig - 1813
4. Cajamarca - 1532
5. Tours - 732
6. Adrianple - 718
7. Vienna - 1529
8. Yorktown - 1781
9. Waterloo - 1815
10. Vienna - 1683
For me, the battles of Tours, Adrianople, Vienna were about survival of races. The arab world would have dominated western and eastern europe. Stalingrad changed the outcome of ww2 and gave the west time to prepare resources to other regions.
I don't think Hastings was that influential. The language didn't begin as a consequence of Hastings in fact it was a successful french invastion. The nobility of england was french and kings such as Richard I didn't even like england. The vikings and saxons continued to live in english society particularly in eastern england and the north and it was in these rural communities away from norman control that english as a language grew. The development of the long bow as a military weapon changed england as a nation not the battle of hastings.
Battle of the red cliffs?