Someone who is unnaturally adept at propelling small objects at smaller targets with great skill and accuracy, most often in sports, I.e. Soccer, hockey, lacrosse, and football, or with an actual sniper rifle. More general uses are those who can fling small pieces of debris at trashcans, teachers, peoples' heads, eyes, exposed cleavage, and balls with great accuracy and velocity, thus causing general mayhem and annoyance.
Common projectiles include: trash, balls, gum bands, pencils, pens, soccer balls, footballs, hockey pucks/balls, sticks, food(carrots), cards, cd's, bottle caps, etc. You get the point.
Common targets: head, face, eyes, junk, cleavage, goals, trashcans, teachers, etc. Anything that shows you have done skill.
, did you see that shot?! He's a freakin' sniper!
Whoa, did you really get that in the trash from here? You're a sniper.
I totally just sniped him in the junk
from here with that ball.