"invest option", I usually invest money as house fund, betking, just-dice and yolodice are my favorite sites because of this feature.
"affiliate program", this one is good for my own pocket, I can make profit by referring new players, honey program.
"security(2FA)", this one is a must feature, I refuse to play in non-2FA sites, it is extremly insecure.
Agree on the 2FA - it has to be a must these days!!