Damn, so many themes that are classic.
I guess I'll go with
1. DX - The way the beat started off with "Are you ready?" then dude talkin slow and quiet, then it just erupted into "BREAK IT DOWN!!!" is just sick.
2. Gangrel - Shit is just fuckin sick. Loved that fuckin theme.
3. Tazz - I marked for it during the ECW ONS stuff. Just a classic.
Honorable mentions go to all of HHH's themes, John Cena's Basic Thuganomics, Stone Cold's, Evolution's, and Batista's OLD theme before he got a crappy watered down version with words.