High dose alcohol of course causes back outs but the worst black outs i had were from Zolpidem or Clonazepam, those weird drugs made me go to bed sleeping then getting up sleepwalking and finishing the fucking boxes of the meds themselves and doing a lot weird shit.
Is not that difficult to black out on Ketamine and alcohol combo, even at moderate doses, but that kind of blackout is strange cause you sometimes could remember some blurry sensations and the peculiar feeling of total mindfuck that the combo usually gives.
I also blacked out a couple minutes on a combo of DXM and benzos waking up later on the ground with lots of people around after crashing my scooter in a pole on the side of the street without even trying to press the brake, my friend told me, scary.
So all my black out stories involve either alcohol, benzos or benzo like drugs. Those drugs have something sketchy.