Knob Creek, named after a creek near where Abraham Lincoln grew up, is one of the four "Small Batch Bourbons" produced by Jim Beam (the others being Basil Hayden's, Booker's, and Bakers). These four, along with Maker's Mark, are generally considered to be the "middle class" of bourbon; vastly superior to Jack Daniel's, Wild Turkey, Old Granddad, and friends, but not falling into the extremely expensive, specialty range. The major selling point for Knob Creek is that it is aged for 9 years (most bourbons are aged between 4 and 8 years) in charred white oak barrels, which (supposedly) gives Knob Creek its excellent smoothness and flavor (I am willing to attest to the taste, just not that it is due to the length or manner of aging). Bottled at 100 proof, Knob Creek is strong, but extremely smooth. It has a noticeable sweetness, but the sweetness is not cloyingly strong, as I find many cheaper bourbons and whiskeys to be. There is also a distinctive taste of wood in both the bourbon and the aftertaste, which I find quite enjoyable.
When I first started drinking it, I had problems sipping it straight, because while it went down easily, my stomach didn't react well to large amounts of 100 proof liquid being poured into it. I've found the most satisfying way to drink this is to drop a few ice cubes into a glass with a good amount of Knob Creek, let the ice melt, and then slowly sip it out on the balcony in the evening. Rather than being a fast way to get drunk, it's a slow, sort of contemplative experience. It also works well mixed, especially in stronger drinks where there is less mixer to hide the taste of the bourbon.
Others find Knob Creek a little strong, with one review1 going so far as to say "Knob Creek burns in such a way that the drinker is torn between being proud of having swallowed it and the urge to immediately wipe the taste from memory. The flavor reminds you of the very pain that alcohol supposedly undoes, elusive to the degree it is intense, unremitting[...]". Others are quite a bit more positive than that, and it won the title of National Champion Whiskey from, of all places, Wine Enthusiast. And The Book of Bourbon called Knob Creek "as close to perfection as any bourbon on the market."
A 750 ml bottle of Knob Creek will run you between 20 and 30 US dollars, and is well worth trying for anyone who enjoys a good bourbon.
1: http://missionliquors.com/bourbon/knob-creek.html