So does 10 mg zolpidem tartrate. As in, totally prevents memory formation. Gotta be careful with that stuff. And prototypically, marijuana. Back in the day, I'd always see movies stoned. That way, if I liked them, I could see them again freshly. And if I didn't liked them, I could forget about them more easily.
Brain injury can also obliterate memory abilities. I've had a single moderate concussion, where one of my first memories afterwards is of sitting in the hospital emergency room with a couple friends. I had a notebook with my handwriting, containing several pages of questions/answers that my friends had me write down so they could stop repeating themselves to me.
I think any kind of shock/adventure can mess with memories. I was in a nasty car accident about half a decade ago. I escaped virtually un-hurt (just some bruises and bumps all over). I can only remember flashes from before and after the accident.
None of us in the car can recall what actually happened (even the driver!). One moment we were cruising smoothly at about 100km/h and the next moment I'm crawling out through the windscreen, because the car is upturned and the passenger window is crushed closed.
None of us had anything more severe than a few bumps and a couple of scratches in my palm from the broken glass. But none of us can clearly remember how it happened, how I called for help on my phone, how we were taken to the hospital.