6wts.......

General purpose troot rod.

I have a 9 foot 6 weight Hardy that I use quite a bit during the first half of trout season. I enjoy fishing streamers, which it throws quite well, and it handles weighted nymphs with a few shot better than the 5wt. I use an older, moderate action 9 foot 6wt for throwing foam bass bugs when I fish for smallmouth as well. I think the hardy could handle a steelhead, but being more of a trout rod I put a click and pawl reel on it, not something I'd like to use against a steelhead.

I have an older Powell American made 6 wt that I love to cast.  It has a fighting butt and is great for bass, steelhead, and for times when I want to get out there a little farther when fishing ponds.

I use mine for smallies (with smaller flies), throwing streamers, and bonefish when I get the chance.

i bought my winston 6wt. specifically for smallmouth fishing but also use it for trout fishing the clarion river if the smallies aren't biting.
oh ya, and for competition events

I use mine for river fishing for bass, saugers, walleyes, stripers and anything else that will take my fly.

I have used mine for just about everything that I fish for. It's like a 5 wt, a good general rod with a little more backbone. I've used mine in salt, for bass and for steel. Of course there are more specialized rods for different conditions but the 6 wt id a great all around rod for medium sized fish.