Barra de la Cruz
Barra de la Cruz is one of the all-time sickest spots in Mexico (tempted to not even share it) but the fact that there's no Wi-Fi, no AC, lots of mosquitoes, only rustic accommodations, and nothing to do besides #surf will keep most people away.
You can get there by taking a pescadera from Huatulco. It takes a swell of at least a meter for the point to work. Unbelievably fun and pumpable wave.