Turnoffs in the dating scene are probably the same as turnoffs in social life. However, married people or people in a committed relationship probably can't do anything about the turnoffs they encounter.
So here is the place where you can list those things that would turn you off if encountered in a date or prospective date.
Dirty teeth (never heard of a toothbrush?)
Bad eating manners (A lot of first dates are in a restaurant; ever wonder why they are the last date?)