Taken from June 2005's Total Guitar:
Total Guitar:... Are there any modern players who excite you?
Tom Morello: There are a couple of guitar players i really like the sound of. Omar (Rodriguez-Lopez) from the Mars Volta. Rage toured with At The Drive-In and I remember watching him play and going, "That's crazy". I also enjoy the fella from Muse (Matt Bellamy). That guy has some very interesting ideas. He's not afraid to rock and is truly innovative on the instrument.
Tom Morello is Matt Bellamy's guitar idol, for the record :)