try odd meters, 5/4 is a good one. It's the "mission impossible" time signature, or the "Take five". You also have the 7/4, which basically is a 3/4 followed by a 4/4 that's the floyd's "money" time signature.

Then you have the minor harmonic, the diminished scale, the whole tone scale (very cartoon-like, I love it). Try experimenting with slides, open tunings, string your guitar upside down, nashville style (only small strings, EAD are an octave higher)... Listen to styles you don't listen to normally, it will come up in your playing.