Memorization of historical facts doesn't seem to be as common in school as it used to be, but I still remember two specific things I learned from my freshman world history teacher, old Mr. McLearn (yes, his name was really McLearn, he used to joke that it should be McTeach).

1. Charles Martel defeated the Muslims at Tours in 732.
2. William the Conqueror of Normandy wins the Battle of Hastings in 1066.

I can't say that I remember any one particular thing that any other teacher taught me, so that memorization thing must not be too awful.

As already stated by GTH, the world as we know it would likely be vastly different if the Muslims had taken over the rest of Europe, so Charles Martel easily gets 5 stars.

We owe a lot to old Chuck, and we should reflect on him from time to time. If the Mohammedans would have triumphed at Tours, our society would be in a sad state today. Scotch whisky would never have been invented. That would be a real loss! There would have been other deprivations also, I am told.