I went through most of my entire first game with the misconception that Tool boards, workbenches, and, most notably, "Stuff"s could never actually hold items. Yes, that means that I missed out on 50% of the inventory in San Fran, and almost all of Buster's. (although I still wonder why his shop sells crap like rocks)
I showed Fallout 2 to a friend of mine, and meant to give her a crash course in making a character that wouldn't fall on its ass, but she insisted that she experiment herself, so I let her go. Needless to say, she did some incredibly silly things. For Example, tagging Barter, First Aid, and Repair, taking Bloody mess and something else inane, having a high ST and a low PE, etc, etc, etc. Needless to say she didn't finish the game with that character... I showed her Per's guide once day, and dawn came like a nuclear airburst.