A very brief, minor moment in the same episode when Thunderbird 1 approaches and one of the personnel has to sit down in disbelief when reading its speed. It really shows off how ahead of their time the Thunderbirds are.
The Firefly's appearance in 'City of Fire', and just how much punishment it can take.
Thunderbird 1 being shot down in 'The Uninvited'. Similarly, Thunderbird 2's crash in 'Terror in New York City'. They are played completely differently: The first comes straight out of nowhere and is played for pure shock value. The second is a drawn-out sequence that shows the beloved big green 'bird get utterly thrashed.
In Vault of Death, Scot and Virgil can't cut into the vault door, and the only key is too far away. They go into the subway to cut through the wall instead. Meanwhile Parker, outside the vault, asks lady Penelope for a Hairpin. In the time it takes Scot and Virgil to cut in, Parker manages to unlock the state of the art door using nothing except that one hairpin
'30 minutes after Noon': Scott dropping the explosive bracelets in the ocean just as they are about to explode.
In "Attack of the Alligators", all the problems of the episode get solved the moment Thunderbird 2 shows up.
They scare the mutant "alligators" (really crocodiles) away with the landing gear (the smoke and the fire), gun down the retreating alligators then send Thunderbird 4 to retrieve the last chemical from the river.
Virgil saving Lady Penelope in 'The Perils of Penelope'.
The Tracys rescuing the crew of a Russian oil-rig that's exploding at the beginning of the film- the crowning moment being when Jeff orders Thunderbird 1 to initiate "knockdown procedure"- meaning Thunderbird 1 fires a missile at the center of the blazing inferno, extinguishing it immediately.
Tin-Tin, Fermat and Alan heading into the River Thames to rescue the passengers of a submerged monorail (The Hood having severed it while using the Mole to drill into the Bank of London)- Alan takes Thunderbird 4, but Fermat can't get a clear lock on the monorail with Thunderbird 2's winch hook- Tin-Tin dives in from hundreds of feet above the water to lock the hook onto the monorail, and nearly passes out before coming aboard Thunderbird 4. This quote sums it up:
Alan: We're the Thunderbirds. Our duty is to save those people.