I'll have a sandwich
You're in the middle of a dumb conversation and someone decides to randomly ask you for your opinion. You say 'I'll have a sandwich' and pretend you're not even there anymore.
At the grocery store, some guy starts talking about his dog. I say 'I'll have a sandwich' and walk off.
My neighbor comes over and starts telling me about his job. I say 'I'll have a sandwich' and go eat.
My friend asks me what I think about the new movie. I say 'I'll have a sandwich' and leave.