"The Fallen", the Leitmotif for the eponymous character, stands out for being an extremely creepy and alien combination of measured synthesizer beats and human voices. It shouldn't work, but it does, and the end result is both awesome and a prime example of Hell Is That Noise (and potential Nightmare Fuel).
It's easy to see why Lockdown's Leitmotif was chosen as the trailer music. It's the eerie, discordant track that plays as he stalks out of the smoke and ends your life.
The Main Album
"Your Creators Want You Back", a reprise of Lockdown's theme which play's during his capture of Optimus. It nails the terror and sadness of those involved perfectly.
"Dinobot Charge" is an amazingTriumphant Reprise of the Decision suite. Six and a half minutes of giant robots riding to the rescue on colossal metal dinosaurs doesn't usually get much much more awesome than it already is, but inclusion of this track manages just that.
"Honor to the End" plays during the final showdown between Optimus and Lockdown. And it is incredible.
Nothing's Gonna STAND IN OUR WAY! It's like something right out of a Metal album cover: "Killer metal sharks hacked to death with a band saw, transforming robot turns into a sports car, fights a giant octopus with lasers and all played out to the backing of some classic 80's hair metal. Is there anyway of packing in any more awesomeness into 2 minutes!?!"
The Unicron Medley is perhaps the polar opposite of the Transformers theme, being slow, sinister and mysterious in contrast to the upbeat, to the point nature of the main theme. And it is AWESOME.
NRG's Instruments of Destruction gives the Decepticons some truly badass music to mow down Autobots to. The song's climaxing with a metal scream as Megatron blows Ironhide away is particularly awesome.
Transformers Cybertron had an awesome soundtrack, although the original Japanese version, Galaxy Force, and the US version (which was mostly unchanged, with a few exceptions such as the exclusion of the Japanese vocal songs) have individual fan bases.
Most of the soundtrack, but special mention goes to the theme and "We Have Returned". Regarding the theme, there are no words whatsoever, yet they somehow manage to fit all the epicness of the series, no, the ENTIRE TRANSFORMERS MULTIVERSE in one 44 second long song. Even if you don't like the show itself, there's a pretty good chance you'll like the song anyway. And that five-note pattern repeated in the song? It's the godamn classic transformation sound, turned into a song.
In Japanese Dub, the second opening theme "Transformerz" by m-flow an Rap/Hip-Hop theme and the third ending song "Discord" by Tokyo Girls Style.
Transformers: Prelude to Energon has an extremely memorable soundtrack, especially the boss themes. Then there's the extra theme song remixes unlocked by collecting Data-cons. The ending credit song by The Brown Hornet puts a funky spin on the original theme song. The lyrics make this song even more awesome.
While Beast Wars: Transmetals was a pretty bad game, it had this gem.
Transformers: Devastation: Since the game was developed by none other than Platinum Games, musical wonders are ensured to happen. Being composed by the same guy who did the music for the 1986 movie doesn't hurt, either.