While we have an x-com thread here, I would like to propose my rookie pistol theory.
We all know that rookies are so fucking helpless that they can't hit something that's like four paces in fucking front of them, so even in close-quarters fights in UFOs they routinely fucking fail. This leads me to the conclusion that one should run them right up to the alien and have them cut loose point-blank.
Second- rookies have very few TUs, so closing to point-blank and still being able to fire is a problem. However, since pistols have very low TU requirements to fire, and since the point-blank thing solves the problem of their piss poor accuracy, they're perfect for close-quarters fights.
Third, rookies are much better with grenades then they are with guns of any sort, and pistols means they can hold a nade in one hand with no accuracy penalties.