To be honest, I don't think I have a favorite stream. Growing up in northern Michigan, working in a flyshop in Idaho, and then working for an airline has allowed me to fish in as many different places as the rich folk. Here's some of my favorite streams:
Pere Marquette River in Michigan: my original "homewaters" great fishing for big browns during the hex hatch.
Silver Creek, Idaho: Amazing fishing during the brown drake hatch
Green River, Utah: Sept. fishing on a rainy day is superb! The rain drives all the yuppy idiots off the water and the blue winged olive hatch really makes the fish easy to catch.
Humptulips River, Oregon: October will show you the biggest silver salmon you've ever seen. Really easy to sightfish to fresh runs when using a single egg pattern.
Stave River, British Columbia: October has a killer Chum salmon run. Since it is C&R, you got it to yourself and it takes 1/2 an hour to land each one!
Mousum(sp?) River, Maine: Stipers(schoolies) on a 4wt. is a BLAST!
Jim