I'm a bit surprised that no one has mentioned the 70-200 2.8 IS. You mentioned shows and if those include low light the 5D3 + the 70-200 is a great combo. I have a 100-400 and use it a lot on both my 5D3 and my 7D, but it's better in good light. I also have the 17-40 that several have mentioned and I agree. it's a great lens and I didn't realize its full potential until I went full frame.

Good Shooting,
Mark