Great question - video gamers are a dealbreaker for me. 

The cliches of seemingly hating women are always red flags: talk badly about their mother, ex, etc.

I want to think of a single-handed dead-no, though, that would maybe come up... gotta be something specific. 

Talking about your ex is top of my list. Boring, with no humor is also a no go for me.

Ah, I thought of it. When men are weird about the bill on a date. That's always a dead sign. Bad tippers are unattractive, too. But I've had guys not even buy my drink, and I just know right then.

Come to think of it, I met up with a guy from an app. Good looking but too short for me, but I gave it a try anyway, but then I ended up embarrassed by the way he treated the staff at the restaurant, not to mention as a foreigner who couldn't speak the language. I take being a good guest seriously.

I agree with what has been shared. I wouldn’t want a first date to be bad mouthing anyone, and I would not want to see a harsh judgmental person. Being able to smile and laugh is essential.

I am very traditional/old fashioned so I would like to receive some chivalry. It would be such a bonus if he would open/close my car door and did “ladies first” gestures.

Because I’m old fashioned I must admit that I would be offended if he didn’t offer to pay on our first date. I would assume he didn’t think I was special/worthy so I guess this would be a deal breaker.

Impolite to waitstaff as I've been in service industry my whole life. Don't embarrass a Capricorn.

Also there has to be a 'spark'. No point in wasting anyone's time.