CLEARED FOR TKOF AND ABOUT TO CROSS RWY HOLD LINE; B737-700 MUST BRAKE AGGRESSIVELY TO AVOID C206 CUTTING IN FRONT OF THEM TO ACCESS RWY. LCL CTLR CANCELS B737 TKOF CLRNC AND CLEARS C206 FOR TKOF.

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WE HAD BEEN SITTING AT THE DEICE PAD AT THE APCH END OF RWY 28R FINISHING UP SOME CHKLIST ITEMS. WE WERE ANGLED 45 DEGS TO TXWY A WITH THE NOSE OF THE JET FACING THE FINAL APCH END OF RWY 28R. WE WERE MONITORING TWR FREQ; WHICH WAS EXTREMELY BUSY WITH ARRS AND DEPS. WE HAD JUST FINISHED UP WHEN TWR ASKED IF WE WERE READY. WE SAID YES AND WERE SUBSEQUENTLY CLRED FOR TKOF. I STARTED TAXIING STRAIGHT AHEAD; CROSSED THE HOLD SHORT LINE OF THE DEICE PAD; AND WAS ONLY APPROX 25 FT FROM THE YELLOW CTRLINE OF TXWY A (STILL AT A 45 DEG ANGLE TO IT AND WAS NOT ABLE TO SEE THE C206 SPEEDING TOWARD US). SIMULTANEOUSLY; TWR CANCELED OUR TKOF CLRNC AND MY FO SAID THERE WAS AN ACFT BEARING DOWN ON US. I HIT THE BRAKES AS THE CESSNA CUT IN FRONT OF US. HE MISSED US BY APPROX 25 FT. WHETHER HE WAS MONITORING TWR OR NOT; HEARD OUR BEING CLRED FOR TKOF OR NOT; HE 'SHOULD' HAVE SEEN US TAXIING TOWARD THE RWY. EVERY SEAT WAS FILLED IN HIS ACFT AND IT WAS TAXIING AT APPROX 25 KTS. MY FO ASKED TWR IF HE WAS GOING TO STOP AND TWR SAID THEY WERE NOT SURE. TWR CLRED THEM FOR TKOF AND I ASKED TWR IF THEY WERE GOING TO SAY ANYTHING TO THE CESSNA AND THEY SAID THEY WERE TOO BUSY. SOMEBODY REALLY NEEDS TO TALK TO THAT PLT (IE; FAA) OR HE IS GOING TO HURT SOMEBODY. THE FAA REALLY NEEDS TO TALK TO THIS PLT TO EXPLAIN HOW SERIOUS THIS IS AND HOW BAD IT COULD HAVE BEEN. I HAD TO HIT THE BRAKES WITH 127 PEOPLE ON BOARD AND HE IS STILL PROBABLY CLUELESS ABOUT HIS ACTIONS.