Three way tie between WOTM, Dividing Line and the Albert Mohler show. I really can't choose which I prefer more. Each of them offer something a bit different.
These guys are awesome. John Lofton might be the gutsiest, hardest fighting Christian radio personality. He has a devastating dry wit, too (not for the faint of heart).
Michael Peroutka is an astute voice of law and its' relation to God's word.