All good answers.
If 'only one,' (specifically) the Sage 8100 xp. Over gunned for somethings, under gunned for others. But you can handle very large fish on an 8wt ... and still have fun with smaller summer runs if need be.
A 10' 8wt seems to be the major rod of choice with the best one-handers here on the Rogue for year round fishing.