Dragon Soul, the first opening theme, accurately captures the spirit of Dragon Ball with a modern spin. It's also one of the catchiest theme songs you'll ever hear. When Bulma and Mister Popo take Kami's old spaceship for a test run, it's accompanied by the orchestral version of "Dragon Soul", which transitions smoothly into the Eye Catch. Did we mention that it's sung by the voice actor for GOKU HIMSELF?! (The DVD sets change who performs the song; Vic Mignogna's version is the one used for the TV episodes.)
Dragon Ball Z Kai wouldn't be true to its namesake if it didn't have some epic music, one of which is the Orchestrated version of "Dragon Soul". Not to mention the brief rock/metal music that plays while fighting Frieza in episode 40, Only a Chilling Elegy... Frieza's new theme song. It contains Ominous Japanese Chanting followed by rock music. The opening also plays in episode 37 when Frieza impales Krillin.
SAIYAN BLOOD. Makes Vegeta charging his power up before fighting Frieza into a moment of pure badassery.
One Hit to Victory, the absolutely epic music that plays as Vegeta prepares to use Final Flash against Cell.
Yushi no Gaisen translated as "The Braveheart's Triumphant Return", one of Goku's themes. Used for his "I AM" speech, and this time it was accurately dubbed as well
Kyousha He Idomu Yuushi, translated as "The Braveheart Challenges The Strong", used in pretty much any scene where the good guys start kicking butt.
An Isolated Warrior lets us know that the heroes are done warming up and things are going to get serious.
Once Kai reached the Android saga, the music quality jumped way up, with the Vol III OST. Songs that range from epicadventure and thrill to suspense and despair.Courage Fills The Heart is a strong contender for most Heroic thing EVER.
The Lone Warrior ups the awesome quotient of Trunks powering up to square off against Cell PAST eleven.
Kuu-Zen-Zetsu-Go, the opening theme of the Buu saga's Japanese broadcast, kicks things up a notch with a lightning-speed tempo and energetic guitar riffs that get you sufficiently hyped for the episode itself. It acts as sort of a sequel song to Dragon Soul, much like We Gotta Power from the original DBZ acted to Cha-La Head-Cha-La.
Trapped Between Past and Present plays when Vegeta asks about meeting Goku in the afterlife and learns that he would be reincarnated in Hell.
Stay Away From Me happens during the first Super Saiyan 3 transformation, ending with The Chosen Warriors (the first attempt with summoning the Super Saiyan God). The song plays again during Episode 66 of Dragon Ball Super when Vegito makes his triumphant return.
"Fight It Out!" and "Never Give Up!", the opening and ending used for the show's international broadcast. Like "Kuu-Zen-Zetsu-Go", the former also works as a sequel song to "Dragon Soul", and the Gratuitous English just adds to the charm of both.
"Let It Burn" plays as a fitting "final boss"-like theme during Goku and Kid Buu's fight on the Supreme Kai planet, especially when the intensity of said fight starts to horrifically change the world.
Vegeta's Sacrifice/Respect plays at two vital points of Vegeta's Character Development in the Final Chapter; his intended Sacrifice and his newfound Respect for Goku. This triumphant, heartwarming song makes a third reprise in Super when at the end of the series, 17 wishes for all the erased universes to be brought back to existence.