My most recent death though was i was looting an area that had some radiation. I didnt realise i had 1000 rad and died and i sat there for a while wondering what happened.
I had that happen to me
twice at Vault 87 on one playthrough. I was so intent on getting close enough to the Super Mutants to drop Nuka Grenades on them that I didn't check my rads, and in all the noise I couldn't hear my Geiger counter.
First time I just keeled over dead for no apparent reason. I went "WTF", reloaded and promptly died again. It was then that the cluebat hit me. :facepalm:
And I even knew about the radiation levels at Vault 87. I just completely forgot about them in the heat of battle.