I think it’s time for a classic, the speech that is said to be the defining speech of World War II: "We shall fight on the beaches" by Winston Churchill. Unfortunately I couldn’t find a recording of the full speech. So I’ve included a YouTube video, an audio file and the full transcript.
The audio file can be found at The Guardian. You’ll find several speeches when you follow the link. Just scroll down to the first section, entitled "No. 1: Winston Churchill", and click on "Listen to the speech".
The video doesn’t include the last section of the speech, which is, in my opinion, the most important part.
The full transcript can be found at FiftiesWeb.