I Have not been on many coasters, but I would have to say
Cyclone - SFNE
DON'T RIDE IN BACK!! EVER!!!
Mind Eraser - SFNE
My right ear was bleeding when I came off the last time I rode it
Boulderdash (2006) - Lake Compounce
Back in 2006 before they reprofiled BDash, It was one of the roughest rides I have been on, the non banked turn after the first drop - ouch