4. Catherine
https://www.youtube.com/watch?v=HPFH34mO6Ds Catherine doesn't employ any technical wizardry to screw with your head, it simply asks you a series of short questions. These questions include "Does life begin or end with marriage?", "Who would be responsible if you cheated, you or the person you cheated with?" and the ever-challenging "Could you have sex with an attractive ghost?" During the course of the game you're asked dozens of questions like this. Some are silly, others are very, very serious and introspective. It becomes especially awkward if you happen to be playing the game with your significant other. There's a good chance that relationships have been strained by some of the questions asked in Catherine, that's how personal it gets. This is a level of introspection that's very rarely explored in games. Through a relatively simple mechanic, Catherine legitimately forces you to question and reevaluate aspects of your own personality.