KBS is also my favorite beer. It really is amazing.
Don't know if it was mentioned, but if you love KBS (as I do) you should also try to get your hands on Goose Island's Bourbon County Stout when it releases (which was just recently, and may be hard to find now)
Here are some of my favorite beers in no particular order:
Imperial Stouts:
Siren Noire- Heavy Seas, Clipper City Brewing (American Chocolate Imperial Stout) Good when fresh, amazing when aged)
Kate The Great- Portsmouth Brewery (Russian Imperial Stout) I went for Kate Day a few years ago and snagged 4 bottles, drank one fresh, and then again on the year anniversaries for 3 years. The 3 year was absolutely amazing.
Bourbon County Stout- Goose Island (American Imperial Stout) This is the best imperial stout I've ever had. It tastes amazing fresh and I can only imagine how well this beer ages. They also make various flavors such as a coffee version of this stout.
Kentucky Breakfast Stout- Founder's (American Imperial Stout) This beer is a very, very close second for me to the Bourbon County Stout. It's absolutely delicious.
Canadian Breakfast Stout- Founder's (American Imperial Stout) This is similar to the KBS but it is aged in maple syrup barrels instead of bourbon barrels. Hard to get but worth it. Most people say they prefer this one to KBS but I prefer KBS. Then again I love bourbon.
Cherry Imperial Stout- Blue Point Brewery (Russian Imperial Stout) This beer is also a sour and when you can get it on draft (which is the only way you can get it I believe) it is very very nice. Not as complex as the others listed here but very good with only a slight hint of cherry... not at all overpowering and still letting the other roasty notes traditional to this style come through
I was going to list all my favorites from various styles but now I'm bored. I'll come back to it later with some Belgians, Hefes, IPAs and the like.