That is a major turnoff! Also, people who work waitstaff to death.
Ex: I once had lunch with a potential new g/f and she asked about salad dressings.
The waitress named off the usual- ranch, bleu cheese, thousand island, vinegrette and the house dressing. I can see asking to sample the house dressing, but this woman asked the waitress to bring her samples of ALL of them--during the lunch rush.
Then she chose ranch. On a small side salad.
She also asked questions about the rolls, the ingredients of several entrees and the entire dessert list.
Being overly late. After 15 minutes is bad. At 30 minutes, I cancel.
Another turn off is bad grammar. Supposibly and irregardless are the worst.
Borrowing without returning, returning things in wrecked condition--basically everything my pushy new next door neighbor says or does.
One quirky turn off I have is people making "air quotes" with the fingers.
Sharing details of our sex life in a group of people, in an attempt to be funny.
Needless to say, nose-picking, intentional belching and farting, or doing the usual bathroom things with the door open. I don't need to see anyone on the toilet, flossing, or otherwise spoiling the mystery of her beauty.
Finally, the silent treatment or ghosting without any explanations.