How could I make an attack that hits the first target it contacts?

[PaladinHeart]

I'd like to make a more realistic type of map, so is there a way to make the attack hit the first damage-able unit that gets in the way?

I would also like to have an ability that makes the unit's primary attack hit randomly (being more or less accurate, based on the ability's level) but I'm not sure how to do that, if it can be done at all..
I know this can be achieved with the critical hit skill, but it does not account for missed shots. They should go somewhere.

 

[HydraRancher]

Use an ability triggered by the A key that causes the hero to play an attack animation. Detect any units in front of it to take damage.

 

[GFreak45]

you can also create a dummy unit that moves along the path of the projectile at the same rate (use xspeed to attain higher than 522 MS) and when it comes into range of a unit deal damage to the unit and destroy the dummy, so it only hits 1 target max