If you're a sneaker, use silenced weapons. For one handed, you can use a stock silenced .22 pistol which is cheap, but weak... or a 10mm pistol you equip with a silencer. The "Professional" perk (+20% to sneak crit damage with one handed guns) helps alot. Later on in the game you can find or buy a stock silenced .22 SMG, which is awesome for stealthy kills.
Silenced weapons are best, as they allow you to kill enemies without getting gang-rushed by everyone near enough to hear the shot. It also lets you kill faction members without losing rep with that faction. (Must stay in sneak the whole time and make the kill while "HIDDEN.") For example, I've wiped out three legion outposts with silenced weapons, and the Legion is still neutral to me. :laugh: Also found this really helpful against the Powder Gangers and in Primm early on.
For long range, go grab yourself the Ratslayer - it's a unique Varmint Rifle variant which comes equipped with all the mods, and is outstanding for long range one-shot kills. Just remember to shoot 'em in the head - it's more sincere.

I keep hearing people talk about the 'sniper rifle' and how It's the greatest thing since sliced bread.
My question is, where the eff is it? I've got a sniper-style char, but I'm limited on what I can do because the game has an invisible wall for my bullets outside of VATS range.
It's pretty good too - first one I've found is at Camp McLearen (sp?), on one of the bunks in the tent with all the sniper/recon guys - and taking it isn't considered stealing. Still think I prefer the Ratslayer or a pimped out Varmint Rifle... easier and cheaper to repair, and lots of ammo for 'em. Of course, once you start bumping up against Deathclaws and heavily armored foes, yeah, time to pull out the sniper rifle.