Whether performing in Rage Against the Machine, Audioslave, or any of his other projects, Tom Morello always does something unique with his guitar. 

Gibson.com states that his riffs are influenced by Led Zeppelin, Black Sabbath and other classic styles, combined with hip-hop, while his leads and innovative use of effects have no obvious direct ancestry: they’re pure creativity and inspiration.

As a big fan of Rage Against The Machine, I might be a little biased by adding more Rage in the top 5.  However you look at it,  Tom Morello is gifted guitarist. He adds creativity and originality as well as plenty of attitude.   Agree or disagree he is a hard rocking riffmaster. Here are my top 5  Tom Morello defining riffs.

# 5  Bulls On Parade

#4 Cochise

#3 Guerrilla Radio

<#2 Like A Stone

#1 Killing In The Name Of