When I think about you in this way, I imagine you at your most confident and direct. A powerful person who knows exactly what she wants. And what you want is me. I think a big part of this for me is a need to feel desired. A need to feel attractive and pursued and taken. Think of it like this: I don't want to ask you if I can go down on you, I want you to tell me that I need to go down on you. I want you to tell me that I need to do it right now.
But it's not about any specific physical act, though (though I do really love going down on you). The acts are secondary to the attitude. One fantasy I have is that it's night time, and I'm walking towards my side of the bed (you're lying on your side of the bed). And as I'm walking past the dresser you tell me to stop. You tell me to turn around. And you tell me to pull out my dick for you, or to do something totally nonsexual for you, like to stretch out, or scratch my shoulder, or anything. Then you praise me for listening/following instructions, and tell me i'm allowed to come to bed now.
That's a pretty tame thought. But it hits all the ideas that I think about. It's you just showing me that you're in control. It's you being creative, and initiating an action. It's you praising me, showing me that you love me and find me attractive despite the desires I have (or, even, in a dream world, because of these desires I have). It's me doing what you ask, without questioning it, because you told me to do something and I love you and I have an almost uncontrollable desire to please you.
A big thing I think about is possession. Something like the inverse of some of the things I've said to you over the years. It's you telling me that my dick belongs to you, my balls belong to you, my tongue and my mouth belong to you. That those parts of me, and my whole self exist for you. And that you love that. That you wanted a husband with these kinds of thoughts and desires. That you specifically chose to marry me because of it. "I love how hard your cock gets when you eat me out."
It's about helping me get into a specific state of mind. I spend all day thinking about how everyone else is doing, and trying to make sure everybody has what they need. People at my company, our family. I think to myself "what am I not seeing? what are people not telling me." If you're able to do these things for me, you'd help me get into a state of mind where I wouldn't have to worry about what I'm missing, at all. I wouldn't have to check in on everything and everyone, and I would simply know that I am seeing everything I need to be seeing, and you're getting everything you want and need. Because you explicitly tell me that.
A lot of times, during or after we have sex, I'll check in on you. "How does that feel? Are you okay? Was that good for you?" I want you to put me in a state of mind where asking those questions or having those thoughts seems ridiculous. I want you to cum and then tell me that I'm a good fuck, or that I have a hot tongue, or that I did a good job giving you what you wanted. I want to cum and have you tell me, independently and without provocation, that I'm sexy and that you loved it, and praise me for being nasty and doing everything you needed. Tell me it's okay to relax, that I've earned it. I want you to check in on me.
It's about control and power. I want you to tell me an outfit that you want me to wear to bed. Tell me to put on a specific color tshirt. Tell me to get naked. Tell me to put on shorts but no boxers.
It's about you being confident and specific in what you want, and resilient/aware of the power dynamic between us. A fantasy is you asking me to scratch your back, or get a glass of water, or something small as an act of service for you. And I ask you "what's the magic word" and you say "now." (I told you last night i want you to be a little bit mean, this is kind of what i'm thinking of).
If I'm in this state of mind, and I ask "do you want anything," you saying something like "I don't know" will actually stress me out. If you're in this state of mind, I imagine you as knowing exactly what you want. If you don't want anything, you'll say "I don't want anything right now. If I need something, I will tell you." Or even better saying "I don't need anything right now, in the mean time you should do X." Me asking you what you want is a way of saying "what can I be doing right now that will most please you." And the thing I desire, the thing I crave, is a specific thing to do in that moment. To know that there is one thing you want, that you told me you wanted it, and that I did it. That will de-stress me, help me relax, and put me in the state of mind I fantasize about.
Literally the action you tell me to do could be "nothing" or "just lay there and look sexy." But the important thing is that you are telling me what, in that moment, will make you happy.