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.
The "Apostles of Darkness" theme deserves a mention: a quiet, ominous melody that builds slowly into a magnificent crescendo that fits perfectly with their battles (which can be extremely intense and harrowing if you're new to the game, and even if you exploit every last weakness they have, the last battle with them can still come quite close).
Fridge Brilliance - the manual states that Beasts get a serious terrain penalty in snow, and Harpies get a similar terrain penalty in forests. Why? Beasts wear only a Loin Cloth (and are jungle natives), so they can't perform well when they're freezing their asses off; Harpies are clearly flying troops, which would find it hard to maneuver in an enclosed forest!
Game Breaker: Dragons (troop, not general). They're good against everything except other dragons (every troop is regular against its own) and samurai (their only weakness).
Actually, mages are pretty effective against dragons as well, if utilized properly. A good way to take them out is to put the mages on standby mode, then have a general (usually a mage) that has a spell that takes a long time to cast use said spell. Then watch as mages continue to shoot while melee troops are unable to fight during a general's spell/attack.
Harpies on standby mode also fare well against dragons that are moving around on the map. Since troops standing still get to attack first, this gives them a slight advantage over the dragons.
Averted during the final battle against Madruk, where he doesn't seem to be weak against any particular troop type (he doesn't have his own troops, thankfully). However, shooters (Mages & Archers) tend to perform terribly against him.
In a way, the entire finalbattle seems to avert this, with the exception of Gaul, who uses Dragons. Scythe uses a unique troop type (sirens? ghosts?) that isn't covered in the manual, and Katmando fights solo, like Madruk.
Narm - when casting Sonic Boom, some generals will yell out "Behold, the BOOM of DOOM!" Exceptionally cringe-worthy...
Awesome Music: Some of their other stuff is held in dispute, but some of their songs such as "Cry Thunder" are absolutely glorious.
Base Breaker: Marc replacing ZP is already causing signs of this to appear despite the fact that his voice isn't actually bad at all on its own merits.
Covered Up: "Strike of the Ninja", on Ultra Beatdown, is a cover of a song originally recorded in 2000 by Shadow Warriors, a Theart/Totman gag band (heavy metal ninjas).
Drinking Game: Pick one of the following and take a drink every time it appears in a song: glory, fire, starlight, dawn, tears, fury, evil, pain or forever (more). Pick more than one if you're feeling brave.
No human could possibly drink that fast... could they?
By the end of it there'd be accusations of people digitally speeding up their drinking in the studio.
Face of the Band: Herman Li. An unusual case given that he is neither the lead singer nor the main songwriter. Even so, he's the most well known member of the band due to his over-the-top guitar solos and his unique look.
Internet Backdraft: There must be some internet rule that every YouTube video of a power metal band must have more comments attacking DragonForce than talking about the band in the actual video.
It's Popular, Now It Sucks: Seemingly averted at first when "Through the Fire and Flames" was announced for Guitar Hero III with fans celebrating its inclusion, then the game was released. Presumedly because it did boost their sales.
The band's first three albums received generally positive reviews from the power metal community, and the band was believed to have a bright future. The Guitar Hero spotlight changed all that. Oops.
If you only know TTFAF, or found them through Guitar Hero, donot mention that to a long-time fan.
There's also a DLC pack consisting of three additional DragonForce songs ("Operation Ground and Pound", "Revolution Deathsquad", and "Heroes of Our Time"), which are sure to elicit all manner of delighted exclamations from determined Guitar Hero fans everywhere.
And now, with the inclusion of "Fury of the Storm" in Guitar Hero: Warriors of Rock, there will no doubt be many more smashed plastic guitars.
Serial Escalation: If you think that's bad, add drums, vocals, and bass (if it's even really bass!) in Guitar Hero: Smash Hits. Wonder how many controllers will be trashed?
Actually, "Through the Fire and Flames" is meant to be easier in Smash Hits.
Plus the bass track for "Through the Fire and Flames" in Smash Hits is actually really easy to get through. The guitarist and the drummer might be having a hard time, but the bassist is pretty set as long as he can double-strum the controller.