What do you want me to say? / What can I say?
Expresses resignation, helplessness, or mild exasperation. ¿Qué quieres que te diga? = what can I tell you / I don't know what to say.
—Why didn't you prevent it? —What can I say? I couldn't.
What do you want me to say? The situation is what it is.
—I don't like how it turned out. —What can I say? I think it's fine.