Well, the knife will not go there. A small screwdriver - perhaps. Personally, I used a nail. And I was pretty "held" until I managed to come off. Not to say that it feels too pleasant. At least I have not tried to repeat again during my entire conscious life.
The question was clearly not asked by an electrician. Do not be offended: we are not all electricians. If you plug a screwdriver into the socket, nothing happens: the handle is plastic (dielectric). If you stick a nail, 2 options are possible. If you hit zero, nothing happens. If during the phase, you don't want to do this anymore. Most likely you are not going to carry out the experiment wearing dielectric gloves. With bare hands, in room shoes, in socks, or even barefoot, and the floor is not rubber (it is good if it is wooden or covered with some kind of carpet) ... If there is no floor, only bare earth (for example, in a new house), maybe and kill.
Once, in my childhood, I was wildly curious why it was impossible to stick anything into the outlet. I didn't ask adults questions. I decided to check empirically - I stuck eyebrow tweezers into the socket. In both holes. I immediately removed my hands. After that I remember how beautifully orange sparks fell in that evening in the dark room. We sat without light for a day
Nothing. Unless you can close both poles. After all, roughly speaking, tension is created only in the presence of both plus and minus, and what was nonsense in House, he needed to stick one knife into each hole in the outlet and simultaneously grab them.