...oh and siding with Roy Phillips in the Tenpenny quest...
That's not necessarily a stupid thing to do, although that
does depend on a given character's RP.
I actually didn't really do anything stupid on my first playthrough, since playing the first two Fallouts had prepared me to save constantly as well as to be careful what I said and who I picked fights with early on.
That said, this would almost certainly qualify:
During the siege at GNR, I picked up the Fat Man as instructed and fired at the Behemoth at long(ish) range. My Big Guns skill being low I missed and he was able to close in, so I retreated to the doorway I had come out of. So, he reaches me and starts in with the Hydrant Mace, and I fire the Fat Man at point blank range... :nuke:
...let's just say that didn't end well.
I had
no idea that Friendly Fire was enabled since FO3 was my first Bethesda game. I probably should have assumed it was, since the first two games had it, but this being a different developer I didn't know one way or the other.
I also turned in the component Victoria Watts gave me... :banghead:
In all fairness, there was
no way to know I was getting shortchanged by doing so, since such actions often
are the 'best' choice.