At the same position (180 degree) , hold the bar and shake it rapidly while playing legato stuff ... This gives and indian sitar-like sound... Check Steve Vai for that one.
Dive the bar , and tap a harmonic by your fretting hand's middle finger , then pull the bar , shake it or whatever ... It will always sound cool , check Pantera's Dimebag for this one.
A variation of the above one is to use it with Pinch harmonics instead of tapping or natural harmonics , like Satch.
I remember I've read an article on wierd noises by Steve Vai , I think there's a copy of it on his site ... Check it out , it's usefull.