My closest was leaving TYS. We were cleared to take off from 23L. (I think that is the correct rwy number) As were were about to go into position, tower came on very frantically yelling at as to hold our position. Of course I slammed on my brakes just as a light twin went screaming past our nose and landed on that runway. Tower apologized and informed us that neither him nor approach was talking to that guy. We even looked at final and didn't see anything because he was coming in on a dogleg final from behind us. Luckily the tower was on top of things or we would have been another statistic.