I chose a chaotic good path. Interestingly, in this game, there's quite
enough good to be done that you can still be a dick and be considered
good. Gotta love it.
Got to the rotunda, and chose to sacrifice myself. I ran around,
thinking "oh, this radiation isn't so bad".. Then I found the control
panel and realized I'd forgotten the combination! Aw crap. So I go look
through my notes and such, because I remember that it's something to do
with my mom.. I trigger the very first note I get from dad - the one
where he says "I'm sorry I left the Vault, it's for the best, don't
search for me, etc etc". Then I realize what the combination is, so I
enter it, and, well, the lethal dose of radiation becomes quite suddenly
very lethal indeed. I lose all control while dad's voice continues to
play, apologizing for everything... And then as I lay on the floor,
clearly about to die, the message ends with dad going "I love you,"
seconds before a fade to black.
That really made the first run-through worth playing, and it happened by
sheer luck.

--Aldric