These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Several, including Hironobu Kageyama's "Pray" (by his old band LAZY with him singing the vocals), "Power of Love", and "Soul of Rebirth -Jidai no Kodou ni Nare-", all from Sin.
Wind is High (from Zero) is another good one. And the fun part? The music in the TV series and the first 2 OVAS are composed by Koh Ohtani. Yes, thatKoh Ohtani.
Cargo Ship: Some fans seem to like to ship Hayato with Asurada.
Ensemble Darkhorse: Bleed Kaga was so popular with Japanese fans that he was made the protagonist in the last OVA, despite initially making a few appearances in the TV series. The same can be said (to an extent) with Gudelhian, Heinel, and Schumacher, who had drama CD's of their own.
Game Breaker: Hayato's Lifting Turn skill, which makes him almost impossible to be defeated.
Lampshaded also in the videogames, where the Asurada is usually the best vehicle available for the player.
Hayato comes dangerously close to being this in SIN, especially when he obtains the v-Asurada AKF-0G. The only things that prevented him from being this are a few engine troubles and some badly adjusted machines. The PlayStation game takes it further, Only to be defeated by Shiba at the last second of the final race.
Kaga also skirts the line in SIN, as he tries to control Ogre, which leads into beating Hayato in the final race.
Harsher in Hindsight: In episode 1 of Zero (The episode was released in April 1994), Hayato and Randoll nearly got killed when Hayato first discovered the Zero Zone, their cars collided and Hayato's car went off the track banking in the 5th race in England. A month later, the San Marino Grand Prix happened. It got the point where even the staff have heavy feelings for the scenes.
Hilarious in Hindsight: A handful Cyber Formula vehicles such as the Asurada and the Ogre can morph their aerodynamics to go faster in straightways. Now you have the drag reduction system (or DRS) in modern Formula One that does just the same.
The series has full of them, especially the moments between Hayato and Kaga. Gudelhian/Heinel and Osamu/Bootsvorz also have their moments of these.
A notable example of this comes from the final episode of ZERO, when Hayato and Kaga communicate each other via the Zero Realm during the final race in Japan. It also takes a glimpse of a bit of Kaga's past and the reason why he stayed away from the Zero Realm (his friend was killed in a crash).
Kaga: "Hayato, you are me. You are very much like me."
It Was His Sled: Everyone who's seen the show know that Knight Schumacher is Osamu and he is Asuka's brother.
Moe: Asuka, even moreso in the TV series and first 2 OVAs. Mind you, this was before the term was invented.
Many of the serious crashes but especially in ZERO involving Hayato and Randoll, and Hayato's car crashes through the banking, goes airborne and crashes down to the ground. The aforementioned Harsher in Hindsight event in real life makes it even worse.
In Kaga's background story, Eiji dies in a horrific car crash involving the two and his failed attempts to save him from the burning car, which gives Kaga his trademark scar. This is one of the main reasons why he stopped using the Zero Zone up until ZERO.
Spiritual Licensee: The show could pass off as a modern-day adaptation of Speed Racer with an Formula One motif slapped on it. More obvious when the staff originally wanted to make this in the style of the former.
The Problem with Licensed Games/No Problem with Licensed Games: There are several official games released for the Game Boy, SNES, PS1, Gamecube, PS2 and PSP and doujin PC releases as well, with the games raging from great (at best) to mediocre (at worst). Almost all of them never made it to the overseas although the SNES version was released under a different title called Cyber Spin. Out of these, the best games are often thought to be the four PS2 installments (especially the last one), the Gamecube one, and the latest PC installment, SIN Drei Plus.