Ammunition of almost all types can be manufactured at a tinker's workbench, in batches of up to dozens of each type.

(fallout new vegas + FNVedit bug) Fnvedit seems to ruin the order of formlists. Best energy weapon is also debateable but I think pewpew is good but only 2 shots, AERW 13 (i don’t remember what it called really)prototype is good, Elijahs Advanced LAER is good, Q-35 matter manipulator is good, plasma caster is good, sonic emitter. Once you use fnvedit to merge the formlists make sure to use geck to edit the merged formlist, a 'normal' bullet must be the first item in the formlist or for some reason most ammo loses its projectile. Ammunition is quite plentiful in Appalachia, though for this same reason it cannot be sold to vendors, only purchased from them, and cannot be deconstructed for crafting. Best gun is debateable but anti material rifle is best damage and has really good ammo types.

Ammunition is, as usual, necessary for killing everything that's hostile to the player.

Fallout new vegas ammo types