Get the Machina for the Sniper. You'll have to rely on a full charge, and you will need the SMG (or Cleaner's Carbine, though I believe the SMG is a better choice) for close-quarters combat. The Machina on a full charge can OHK most weaker classes with a shot to the torso. If it has <150 HP, it's done for. You'll get better, and the incentive to take down bigger targets (a fully charged headshot on a Heavy is also an OHK, as long as he isn't overhealed) will have you clicking on heads. This may also make you want to play with the Ambassador as well. It's handy if you know what to do.