I agree with troutbert on his goto 2 rod quiver, and if I could only have one (perish the thought!) it would be a 7'6"/5wt. Plenty of oomph to reach out and handle heavier rigs, but not so long as to be unusable in tighter quarters.
But luckily, we don't have those restraints, so I'm more than happy with my quiver of a dozen plus rods, which seems to grow a little bit every year.