PIC OF CORP BE-90 MAKES WRONG RWY TKOF AT MEM. NMAC.

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WE WERE HOLDING IN POS FOR TKOF ON RWY 27 AT MEM WHEN THE TWR CLRED KING AIR FOR TKOF ON RWY 27 FROM THE INTXN. TWR TOLD HIM THAT THERE WAS A HVY JET HOLDING AND WOULD CONTINUE TO HOLD FOR HIM. WE OBSERVED THE KING AIR'S LNDG LIGHTS COMING TOWARD US BUT I ASSUMED HE WAS GOING TO TURN AROUND AFTER TAXIING FOR MORE RWY; BUT WAS AMAZED WHEN HE BECAME AIRBORNE HEADING RIGHT FOR US! HE LIFTED OFF APPROX 3000 FT IN FRONT OF US AND WAS ABOUT 200 FT HIGH WHEN THE TWR TOLD HIM TO MAKE AN IMMEDIATE L TURN AS HE HAD BEEN CLRED FOR TKOF ON RWY 27; NOT RWY 9. THE KING AIR PASSED ABOUT 400 FT OVER AND 100 FT N OF OUR POS. SUPPLEMENTAL INFORMATION FROM ACN 260598: I ASKED MEM GND TO TKOF ON RWY 27 (THE RWY THAT I LANDED ON) AT INTXN C. I THOUGHT I SAID RWY 9 AND 'C.' MEM TWR CLRED ME FOR TKOF ON RWY AT INTXN C. AGAIN; I WAS THINKING ABOUT RWY 9. I WAS ALSO TOLD A DC-10 WOULD HOLD ON RWY 27 FOR ME TO TKOF. IT WAS OVER 6000 FT FROM INTXN C. I TOOK OFF ON RWY 9 OVER THE DC-10 THE WAY I THOUGHT I WAS CLRED.