Why are you angry /why are you so angry? I've been waiting for five hours / I've been waiting for you for five hours / I've been waiting five hours for you! (i prefer the last, it avoids the duplication of 'for' which is ok, but can sound awkward)

These are grammatically correct, however, I agree with Neil that it sounds better to rearrange the second sentence to eliminate a "for". I have been waiting five hours for you! or, to use the contraction I've been waiting five hours for you! BUT you could keep them the way you have written them, as they are GRAMMATICALLY correct.