I feel like giving my boyfriend an ultimatum.
I am hoping you are just speculating about something now and not serious. What is the situation?
I'm going to tell him that he has to choose between me or his emo friends.  I don't want him spending so much time with them
It's okay to want your boyfriend to spend more time with you, but it is wrong to be making ultimatums like this.  Your boyfriend should still be able to see his friends as long as he makes time for you.  You shouldn't be trying to control all aspects of his social life.
Uh, he should know what I want by now. Ladies first.
You will have a reputation of being demanding and where does that get you? I have found that the sweeter the person you the better you are to be remembered in a good light. Sound good now not to say anything?