Sufyan: You may want to check up on the rules on skill percentages in case that 200% figure got you curious. Your basicTo-Hit-Chance is capped at 95%. You don't need to raise your weapon skills far beyond 100 to get the best possible hit chance against most targets. It is roughly your skill (%) minus target difficulty (%). I'm sure Fallout veterans will chew me out for bad information, but I just want to throw it out there not to buff a skill far beyond what you can possibly ever use them for.
Am I too late for the chewing-out? :)
Seriously though, all non-combat skill checks are effectively capped at 95% AFAIK - so having them higher will - again AFAIK - do absolutely nothing. At least not in Fallout 1 (I think it's slightly different for Fallout 2, although the same rule still applies generally).
Combat skills, especially ranged skills such as small guns, do actually benefit from higher values - but how much depends on your playing style. Accuracy is reduced per darkness level (up to three times I believe), then further reduced by the range to the target, then reduced again if the target is behind cover, and finally reduced some more if you're doing an aimed shot (dependent of course on which body part you're aiming at).
The weapon you're using may adjust the penalties as well, as will some perks related to your combat skill. And yes, the target itself does affect it too (due to its AC value).
I find having my primary weapon skill (e.g. small guns) around 150% is pretty good. That way, you should be able to use a hunting rifle to shoot a deathclaw in the eyes in a dark cave and take him out before he gets to you.
The benefit may be less if you don't do aimed shots, use burst fire, or use close-range combat.
