Hmmm...
1. D-day
2. Monte Casino - THIS IS NOT A PARTICULARLY IMPORTANT BATTLE AS COMPARED WITH SOME OTHERS ARRRGGGHHH
3. Austerlitz
4. Waterloo
5. Marathon
6. Thermophilae - Salamis and Plataea were more important.
7. Gaugamela
8. The Battle of the Red Cliffs
9. Dien Bien Phu
10. Carrhae
11. Teutobergald Forest -
Teutoberger Wald is the German for "Teutoberg Forest".
12. The Seige of Constantinople - Which one? I personally think that the 717 one saved Western Christian Civilization, more so than that silly little skirmish the Frank had off in Gaul, but the 1453 one is, I suppose, at least mildly significant. The Fourth Crusade also could be included here as well.
13. 'Ain Jalut
14. Battle of Qadesh - Is this just important because it is one of the earliest battles about which some details are known, or because it was strategically indecisive - i.e. it solved nothing?
15. Seige of Tenochtitlan
16. Seige of Vienna - Which one - 1529 or 1683? The first is more critical, IMHO, but the second one had a huge effect on the rather sad things that happened to France in the next thirty years.
17. Battle of Hastings
18. Lexington and Concord - Again, not particularly important. (mutters about Americans)
19. Trafalger
20. Actium
21. Stalingrad
22. Malta
23. The Alamo - See #18.
24. Yo Mama Hill!/Other - Oh, I love this one!
I agree with previously stated opinions or even ones that haven't been stated that Syracuse, Salamis, Plataea, Manzikert, Yarmuk, Zama, Metaurus River, Nineveh (627), Leipzig, Midway, Gettysburg, First Marne, Sedan, Sadowa, Noryang Point, Second Adrianople, Carthage (468)...and I'm sure there are many others.