For classic stuff.
That clip for the movie version X 1999 with "X" (X Japan) blowed my mind when I first saw it when I was a kid (I'm sure it did that to a lot of people).
X's OP "eX dream" (Myuji) always gets me excited too.
I get mesmerised every time I see those red balls merge and turn to light in his hand (I don't say these words often).
x openingI might be the only one on this planet that thinks this.
Beginning of "Seishun Collection"s chorus (Morning Musume) reminds me of Dragon Ball GT's OP "Dan Dan Kokoro Kikareteku" (Field of View).

Trivia: The 'GT' in DragonBall GT stands for 'Grand Tour'. Woah~ I just learned that today.

ZARD version is great too. Miss you~

For newer stuff. Here's a few.