tough one these would be near the top of my list.....
YouTube - Nostrum - E-Motion
YouTube - Warris & Fly - Life On Mars (Marrs Remix)
YouTube - Protect System II - Simplicity (House Mix)
YouTube - Encoder - U Give The Love (Don't Stop)
YouTube - Blue Alphabet - Cybertrance 98 (Sean Dexter Rmx)
YouTube - Gate - The End
YouTube - Auranaut People Want To Be Needed

non - hardtrance related would have to be....
YouTube - The Orb - A Huge Evergrowing Pulsating Brain...