saamtheblackavengerput multiple stickies under a sentry then detonate. sentry dead
put 3 stickies under the gun, engineer rescues gun away, charge 3 stickies at new gun spot, boy that sure was a fun first 6 seconds of the uber!
if he rescue rangers it then he's marked for death(i think) and you can easily kill the engie with 1 good scattergun shot/rocket/sticky