If we're going with lenses I own already, I'd have to go with the widest range & brightest glass, which gives me:
16-35 f2.8L II, 24-105 f4L IS, and 70-200 f2.8L II IS
If I could have my choice of lenses I don't own, I'd swap out the 24-105 with the new 24-70 2.8L II, giving me 16-200mm at 2.8.
I could probably be convinced to swap the 16-35 out for a faster prime and/or a macro lens, as well...