Pro'ly my two favorite composers are John [Coolidge] Adams and Philip Glass. I've been liking them a lot more now, because I see their influence in my own compositions. It's just all-around great stuff, to me.
Besides those two, I enjoy very much the works of Steve Reich, Richard Wagner, Frank Ticheli, Jerry Goldsmith, Ralph Vaughan-Williams (As a tuba player, I'm required to:D), Charles Ives, Ottorino Respighi, John Williams, Gustav Holst, Giovanni Gabrieli