Gary Johnson has suggested he might want to run for the Republican presidential nomination in 2012. He was a 2-term governor (of NM), he supported Ron Paul in his presidential bid, he has been outspoken against the war on drugs and has expressed a desire to end the Federal Reserve. I'd like to hear more from this guy!
As governor, he earned himself the nickname "Governor Veto" for vetoing over 750 bills and line-item vetoing thousands more. Only two of his vetoes were overturned by a democratic majority legislature, and he won his re-election by a greater margin than his first in a 2:1 democratic state. He campaigned for marijuana legalization while in office as well, believing it would decrease prison populations as well as end the border violence. He doesn't believe in securing the border, but rather making it easier to immigrate.
He is a true champion of small government and civil liberties. He really should be a more regular guest to the show.