Halloween (1978) - That first person POV of young Michael Myers murdering his sister is one of my favorites. It gets my pulse going every single time.

Jaws (1975) - While not technically a horror movie, the opening scene of the woman swimming at night, getting yanked under by those exploratory bites of an unseen shark, then dragged down and gone forever… That shit gave me chills that took about 35 years to get rid of.