Once I had this obnoxious idea of finishing a whole bottle of vodka, then after doing that had the even more obnoxious idea of seeing just how much I could drink. 25 shots in 3 hours later, giving me a BAC around 0.41 and no tolerance built up (which is above the LD50), I forced myself to not pass out for 6 hours after I stopped drinking, which was spent puking, and I was still worried about dying when I passed out. Didn't black out however. Only time I ever blacked out was when I took 12mg of xanax with no tolerance, but I'm sure I was a bit concerned then too.
Then at the peak of my coke habit, I was really concerned I was seconds away from an OD at the end of blowing through half an ounce in a weekend binge, but despite being very concerned about ODing I railed 6 more big lines and passed out 5 minutes later.
...and finally there was the time I shot 2400mg of oxy in a 12 hour period, with an average daily intake of only half that for the previous few weeks. I don't normally worry about taking massive doses of opiates because I never mix with benzos or alcohol, but that day I thought I might have gone a bit too far and tried in vain to stop myself from passing out after my last 300mg double shot.
I'm more responsible these days.