I find words are important during sex, but really they are at their most important during remote (phone or video eg.FaceTime) sex. Here the words are paramount. I have done a fair bit of this with my wife, but I have also had the opportunity to "eavesdrop" on other people. The most exciting word for me is "cunt", especially when said by an otherwise straight laced conservative woman. I loved reading a sexting text conversation by a platonic female in my life and my eyes popped out of my head, and my cock just popped, when I saw this highly conservative woman type, "My cunt is so wet." The phrase that turns me on the most, whether in person or remote, is the female proclaiming, "I am gonna cum."

Sucking penis, hard/stiff penis, masturbate(ing), ejaculate(ing), pussy, and sperm to name a few

Mine said "give me your cum, I want to feel it."
Man, did I cum hard.

I want you in all my holes was one I will never forget when whispered in my ear in a crowded bar

Unexpected crudeness, particularly from females who are normally quite reserved, always turns me on. When my niece was young, she used to sometimes do a bit of sunbathing in our back garden. One day, she was looking down at her bikini top when she suddenly said out of nowhere "I wish I had big tits like mum". We spent the next couple of minutes discussing the pros and cons of big tits and smaller ones while she pulled down her cups to show me how flat she was. Lovely perky nipples though, and due to the nature of our discussion, I was able to give them my full undivided attention without appearing too pervy. Had plenty of wanks over the years to that memory.