Battle of Tours (Poitiers) comes to mind.
I'll quote these two together since I have the same thing to say about both of them: they are totally played up.
The Battle of Tours seemed to be a great victory for the Franks against the Caliphate, at least from the Christian perspective. However, in reality, the Caliphate hardly even felt it, it was not a catastrophic blow in any sense of the word, nor was it the high water mark of Umayyad expansion it's often said to be. Hell, it didn't "halt" expansion at all, the Umayyads had decided long before then not to enter further into Europe.
There are several reasons for this. The most prominent reason was that north of the Pyranees, the climate gets exponentially colder, as well as becoming more hilly, more heavily forested, and generally a nightmare to manouver in. Considering that the bulk of the Arab armies, and the key to their stunning victories, lay in their large cavalry formations, the ground was disadvantageous to their style of warfare.
Another reason is that, however much the Christians looked down their noses at the "Muhammadins," the Muslims did so twofold in return. To the highly cultured and organized Caliphate, Europe was a backwards place full of smelly barbarians. In other words, they really had no interest in venturing into Europe to conquer these people.
Thirdly, the party that the Franks met at Tours in 732 was not an invasion, nor was it a force of any substantial size. What the Franks fought - and beat - was a raiding party, running sorties in and out of southern France, collecting booty and whatnot. Such was their primary purpose in the Dar-al-Harb, and their expressed right by the Qu'ran; to sieze whatever they could in warfare against the non-believers. This is why, when another Frankish party threatened the Umayyad base camp containing their captured treasure and whatnot, they called off their assault on the Frankish force; their whole mission purpose in France was in jeopardy: the booty.
Ain Jalut was a similar situation. Granted, the Mameluks were the first in the West to halt the Mongol expansion by force, but the force they met was hardly the sort of military hammer they threw at Baghdad, Merv, or Kiev. The force that departed for Egypt was already of a substantially smaller size than your "normal" Mongol outfit, only 20,000, in comparison to the 120,000 that sacked Baghdad, or the 35,000 at Kiev. The Mameluk victory over this force was nearly complete, but again, internal politics are what prevented further Mongol ambitions in the Middle East, not the "decisive blow" of Ayn Jalut, which was again nothing more than a sortie.
