heavy usually easy pickings for me since i main soldier, demo, or spy
but if you really like playing scout and somehow get in a 1v1 with a heavy, shortstop and mad milk combo always be the best combo
if the enemy heavy is enfulged in your mad milk, every damage your deal to the heavy will return to you as an extra health, this will increase your survivabillity in a 1v1
and shortstop will do higher damage than the scattergun in medium range somehow, its.. kinda broken