Doki Doki Literature Club is a free visual novel that presents itself as a totally normal game, where you'll meet some cute girls at an after school club. There's more than meets the eye to this one, though.
Did you ever get one of those chain text messages? You know, the ones that say, "SeNd ThIS 2 !!!FIVE!!! peeple or els u will DIE 2NITE!!!" During my high school years, they became so pervasive that they were more annoying than scary. Horror visual novel The Letter changes all that.