Since everyone is putting more than one favorite, I guess I'll post again...
Guo Wenjing - Riding on the Wind
Joseph Curiale - anything he's ever written.
Karl Jenkins - Adiemus I - IV, The Armed Man
Jerry Goldsmith - score to The Mummy, and especially The Ghost and the Darkness
Stravinsky - Firebird & Rite of Spring (obvious...)
John Adams - Chairman Dances, Short Ride in a Fast Machine, Harmonium, Meister Eckhardt, Christian Zeal and Activity
Ticheli - Sun Dance, Vesuvius, Postcard, and anything similar he will write in the future.
Steve Reich - Eight Lines, Music for 18 Musicians; still checking out his work.