Pff... there are so many...
OK, startin with the easy one: my all-time favorite classic composer is Bach, who was an amazing musician and left us soooo many beautiful pieces... I have many others, but I will stick to Bach at the moment...
As to more modern music: I'm a huge fan of movie soundtracks, and my absolute Hero is Hans Zimmer
He's a genious, really! Soundtracks like Driving Miss Daisy, Rain Man, Madagascar, Batman Begins, Angels and Demons, Pirates of the Carribbean and so on, and so on...
I also love a lot of others, like Morricone, John Williams, Howard Shore, etc...
Gotta love good movie soundtracks