The Noontech Diagnostic Machine -more commonly known as the 'OH MY GOD, WHY THE HELL WOULD ANYONE PUT THAT THING NEAR THEIR EYE'- is perhaps one of the most needlessly tense moments in video game history. Playing on everyone's rational fear of having a needle anywhere near your eye, the sequence is unbelievably stressful.
Knowing that the slightest misstep will result in one of the goriest and wince-inducing death sequences is enough to make anyone stand on edge. Not to mention the precision required to get through the machine without watching Isaac get unwittingly lobotomised.
In all honesty, the scene is one of the standout moments in the game and nearly everyone can recognise. It's excellently done and is sufficiently horrible. That doesn't change the fact that literally, no one wants to experience the disgusting terror of the machine ever again.
Even succeeding at jab yourself safely with the needle is enough to give you shivers.