Nigga Napoleon
First time out of the vault
Bozar, hands down. It uses .223 ammo, which is quite plentiful, especially in comparison to 4.7mm caseless. It's also quite accurate even at the extreme end of it's range. Also if you're the type of person to carry a pistol or rifle as a backup weapons, you can use the .223 pistol (some people prefer sniper rifle or scoped hunting rifle), allowing you to standardize on one type of ammo, relieving you of logistical strain. Plus you can get it for free in the Toxic Caves. To be honest, however, the past 5-10 playthroughs I've been using the M72, which with fast shot, bonus rate of fire, and sniper transforms you into slaughter personified.