|The following is based on Fallout Tactics and some details might contradict canon.|
Buggy is a drivable vehicle in Fallout Tactics.
Cobbled together by a bunch of drunken raiders in a barn! Very unreliable so it's not your ideal vehicle for taking on the might of the wastelands. But it is reasonably fast and maneuverable so it can be used in hit and run tactics against lightly armed enemies.
This vehicle only showed up if the player pre-ordered Fallout Tactics or managed to find out the secret edit one needs to make in a certain document in the Tactics folder. It is attached to a bonus mission called Springfield, where it belongs to a gang of raiders, who in fact, are a ghoul-hating group.
Buggy appears only in Fallout Tactics. There was an upgradeable one meant to appear in Van Buren, the canceled Fallout 3 by Black Isle Studios. It was meant to be of moderate speed and pathetic cargo and passenger space, but be able to traverse terrain other vehicles could not.