The theme tune, which has become a favourite for military bands (see the credits for Thunderbirds are GO! for a good example). Works really well when it kicks in during a particularly dangerous scene.
There are lots of other music cues which were often recycled for budgetary reasons, the best of the bunch being the triumphal Fireflash theme.
Although a lot slower and quieter, "Dangerous Game" from "The Cham-Cham" isn't bad either.
Ensemble Dark Horse: Of all the Thunderbird machines, Thunderbird 2 has the most widespread appeal due to its unusual yet iconic design, versatile functions and bright Green livery. Because of this it's most likely the first thing people think of when you bring up the Thunderbird machines.
"Terror in New York City" (in which Thunderbird 2 is shot at by an American aircraft carrier who have mistaken it for an enemy aircraft) and "Operation Crash Dive" (featuring planes that end up going off course and sinking in water due to engine malfunctions) become harsher to watch after Flight MH370, where the plane went off its scheduled course and crashed into the water, the first of which was never found (and some people suggest the plane was shot down).
Also the beginning of "The Mighty Atom" becomes this when you think of just which reactor went at Chernobyl.
A lot of the Thomas/Thunderbirds parody clips can be this given that a few voice actors from the CGI era of Thomas have appeared in Thunderbirds Are Go.
Idiot Plot: In the Nintendo (Hard) game based on the show, Hood threatens to bombard Earth with meteors in two months unless International Rescue turns the secrets of the Thunderbirds over to him. Ignoring the overkill of this plan, Brains immediately figures out why Hood's deadline is so far away: he needs the intervening time to gather the resources to make good on his threat. And the Tracys immediately discover where he's doing it and work to cut him off. Oops.
Memetic Mutation: The show has become one for ProtonJon's streams, with an edited version of the countdown seen in the opening saying "five" five times over shots of the Thunderbird vehicles with edited "5"s on them playing whenever someone donates $25.
Never Live It Down: Fans tend to give Lady Penelope a lot of flack for her bad driving and her fear of mice despite the fact that these "faults" only appeared in one episode, and in case of the bad driving, she got better at it, as shown in a later episode.
Padding: A positive example to a degree. When Lew Grade insisted that the episodes be hour long ones, the producers had to pad out the time of their first stories already scripted and in production. What they did was add in additional plot twists and character asides such as the trope immediately below which gave the stories a great sophistication than what they thought was possible.
Values Dissonance: The sexism depicting the major female characters has become glaring:
For instance, Tin Tin is rarely much more than a Distressed Damsel. At the same time however, she clearly isn't a full member of International Rescue as we never once see her in uniform; she's a civvy that occasionally helps out. It makes complete sense that she wouldn't have anywhere near as much to do as the Tracy boys. There is the IR uniform she wears in Sun Probe and The Uninvited, however both come early enough into the series to arguably qualify as Early Installment Weirdness.
Even Lady Penelope gets this. For instance, she is prone to Eek, a Mouse!! panics. It's even worse in "The Imposters" when she goes on a field mission in a rural area and she exudes feminine stereotypes like wearing high heels in a swamp. Would it have been beyond the imagination of the writers to think of have her wearing tailor made combat fatigues and custom machined weapons?
Outside gender roles, many of the characters including the Tracys and Lady Penelope were shown to be smoking from time to time. This often caused controversy when re-runs were shown since the 80's and beyond.
Visual Effects of Awesome: The vehicle effects were among the best of their time, and still hold up well against modern CG animation (also true for other Gerry Anderson projects). Save for anything involving water, where, much like most miniature work done in water, the scale issues were pretty obvious. Fire, on the other hand, was a series specialty.
Thunderbirds the movie
Awesome Music: The end credits song by British boyband Busted "Thunderbirds are Go" is one of the few things of the movie that's remembered fondly. Hans Zimmer's score was also excellent, as usual for him- especially his version of the "Thunderbirds March".
Big-Lipped Alligator Moment: Just before the Russian oil-rig workers are dropped off at a hospital in San Francisco by IR, a random kid is seen arriving (with his annoyed mother) with a pan stuck on his head for some reason. He's even credited as "Panhead". This isn't relevant at all and he isn't seen again.
Ensemble Dark Horse: Sophia Myles's portrayal of Lady Penelope was received well, being recognised as true to the spirit of the original character. To a lesser extent, Ron Cook's Parker was praised too.
The song "Thunderbirds are Go", which is played during the end credits of the live-action movie, contains the lyrics "don't be mad please, stop the hating". And considering how universally hated the movie is by fans of the TV series...
In another sense of irony, you could interpret the line "just be glad that they'll be waiting" to mean that the fans should be grateful that the film even got to the big screen at all, considering the lengthy Development Hell it went through.
I Am Not Shazam: Hardly ever is International Rescue ever referred to as "International Rescue" (at least in dialogue, the name is still quite visible on some of the Thunderbird craft and various computer screens). The rest of the time, they're the "Thunderbirds", despite that being the name of the craft, not the organization itself. Could be justified when one considers how a real-life International Rescue actually began operations some time after the original series ended, which might've caused some conflict. Another reason might be that, in-universe, people just called them the Thunderbirds because they didn't know the IR name, and the Tracys and crew then started using it out of habit. (Universal's marketing department didn't seem to get the memo- trailers and TV spots continued to refer to International Rescue.)
Mis-blamed: It wasn't Jonathan Frakes' fault the movie turned out the way it did- it was Polygram and then Universal screwing things up (see below). He and the cast were merely working with what they were given.
The fact that FAB-1 isn't a Rolls-Royce anymore, although in the filmmaker's defense, Rolls-Royce (or more accurately, their owner, BMW) had turned it down, and the customized Ford Thunderbirdwas pretty cool.
Uncertain Audience: The movie is based on a series made for a full family (both adult and child demographic) from the 1960s. The filmmakers made the odd choice to market it more as a typical 2000s children's adventure film - when that generation of kids probably had no idea what Thunderbirds was. What's more is that the series was British, while the film was American.
Visual Effects of Awesome: While the redesigns themselves are deemed creative, but poor as redesigns, the Thunderbird vehicles were positively badass-looking in CGI; the oil-rig rescue (which used a huge 40 foot scale model of the rig, filmed at 100 frames per second much like the original series) and River Thames scene were also impressive.