my advice for the ppl who cant get past lvl 9 as the gun wont work (myself included) in to just restart the game to the beginning i no very anoying but it worked for me. =]
caliber123 for lvl 6 just wait till the target comes down the stairs and then shot the guy with the gun without the target noticing and then kill the target =]
 "6 Differences"){kind=icon}
 "The Several Journeys of Reemus"){kind=icon}
 "Portal: The Flash Version"){kind=icon}
 "Tactical Assassin 2"){kind=icon}
 "Nano War"){kind=icon}
 "BoomsticK"){kind=icon}
 "Temple Guardian 2"){kind=icon}
 "The Last Stand"){kind=icon}
 "Franktown Chomp"){kind=icon}
 "Four Second Frenzy"){kind=icon}
 "Kongai"){kind=icon}
 "Catch A Crab 2"){kind=icon}
 "Bullriding Explosive!!"){kind=icon}
 "Powervox V.3"){kind=icon}
 "Billy Blue Fish"){kind=icon}
 "Multiple Categories Puzzle"){kind=icon}