Jelangkung (aka The Uninvited) (2001)
This was the very first Indonesian horror film i watched in a movie theatre and one of the films that kickstarted the rise of Indonesian cinema. Back then the visuals weren't as good as in foreign movies, but that just added a more atmospheric quality to it. Jelangkung is a very well known game to call upon a supernatural being, and all the ghosts (or whatever you wanna call them) are very familiar to our general knowledge and everyday life. After watching this film, as cliched as this will sound, i just can't sleep alone, and refuse to revisit it again after all these years. It was followed by the equally good sequel Tusuk Jelangkung.