When the Nazis use the Dora supergun against the landed Race starships in In the Balance. The Race assume the shell arcing miles into the sky towards them must be a missile, so hit it with their equivalent of Patriot counter-missiles...the text then unprecedented cuts to a third-person narrator who explains that counter-missile shrapnel works well against thin-skinned missiles...not so much against solid seven-ton brass shells. And then the Race defenders get a moment of Oh Crap before it hits... Bonus: The ship had most of their nuclear weapons on board.
Those Wacky Nazis again, specifically Heinrich Jaeger's Panzer Company, when they fight and destroy several Lizard Landcruisers and Fighting Vehicles, considered one of the best small unit battles ever against the Lizards.
One of the raids of Ludmila Gorbunova. She manages to cause a chain reaction explosion during a raid on a Race camp, getting away with minor damage to just her wings.
Just about anything done by Otto Skorzeny, at least until the cruel reminder near the end that we've been rooting for a hardcore Nazi this whole time.
When Stalin sets off the first human-built nuclear bomb, annihilating a significant fraction of the Lizard armed forces. (Later, when humans and Lizards start taking turns nuking each others cities, it gets a lot darker. But that first human-built nuke is awesome.)
The moment in Homeward Bound when the crew of the Admiral Peary learn the Commodore Perry took five weeks to travel from Earth to Home.