Man... pick ONE? I dunno.
I might pick Dogfish Head, except for the hit-and-miss nature of their offerings. Some are awesome, and some are equally awful.
Davydd's suggestion of Bell's would definitely be in the running. I've never had a Bell's brew that I didn't at least like, and I've had some I love.
North Coast Brewing gets a bid just for Old Rasputin Imperial Stout. I've never had anything else from there, but that one is enough.
Rogue ales are all interesting.
Victory is another. Storm King Stout, you can almost chew it. And they aren't just top fermented, they make a really good pilsner.
Founders, except they are responsible for Old Curmudgeon, which I hate.
I'm going to say Bell's. That is the only brewery where I feel confident shutting my eyes and picking a beer.