"Mannish Boy" (Muddy Waters)

"Mannish Boy" is built upon the prototypical, stop-time blues riff that people think of when they're poking fun at the blues:

Bah-dah-da-dum
(Insert something about your upbringing.)
Bah-dah-da-dum
(Insert a boast about your sexual prowess.)
Bah-dah-da-dum
(Insert a different boast about your power over the opposite sex.)
Bah-dah-da-dum...

And so on.

In the wrong hands, it can be hellaciously repetitive and boring.  But with a master like McKinley Morganfield (a.k.a. Muddy Waters) at the helm, it's electrifying.
The lineage of the song actually starts with Muddy's own rendition of the Willie Dixon tune "Hoochie Coochie Man" (1954), which fellow Chess Records artist Bo Diddley transformed into the stop-time boast song "I'm a Man" (1955), which Muddy in turn responded to with his irreverent "Mannish Boy" (1955).
Although I like the 1955 version, I prefer the hard-stomp 1977 version, recorded with guitarist Johnny Winter for the note-perfect album Hard Again.  What makes this version so great is the well-oiled machine backing Muddy: Pinetop Perkins on piano, James Cotton on harmonica, Bob Margolin and Winter on guitars, Charles Calmese on bass, and Willie "Big Eyes" Smith on drums.  And it's not so much what they do; it's what they don't do.  They keep things loose and simple, giving Muddy space to do his thing.  Smith holds down the same basic plodding drum pattern (not touching a cymbal until the last note) while the rest of the band riffs and shouts away.  Everyone, especially Muddy, sounds like he's having a ball.
I first heard this version in a jazz music appreciation class in college.  The professor was discussing the foundations of jazz, the blues being a major component, and he had his TA play the cut as an example of a single-chord electric blues.  There were the initial giggles from the classroom of 200 teenagers, who no doubt had visions of Calhoun Tubbs (I wrote a song about it.  Like to hear it?  Here it goes...) somewhat fresh in their minds.  But by the time Muddy sang his first refrain (I'm a man!) with Winter and pals shouting in the background like madmen, the whole class began to tilt in Muddy's favor.  By the end, the entire room was stomping and clapping along like we were in some gritty South Side blues bar.  It was a great moment.

"I Got What It Takes" (Koko Taylor)

Koko Taylor (born Cora Walton) got tired of sharecropping and breaking her back, picking cotton down South.  So she and her husband got the hell out of Memphis and went to Chicago in 1952 to find better jobs.  By the end of the decade, she was cleaning houses by day and singing in blues clubs by night.
It was a few years before she got her big break.  In 1962, she was attending a Howlin' Wolf performance, and the Wolf called her up on stage to sing a few numbers (so he could go backstage to get a drink of liquor).  After wrapping her set, she ran into prolific blues songwriter/bassist Willie Dixon, who also was at the show.  Dixon told her he liked her style and promptly helped her record her first single, a Mel Tillis tune called "Honky Tonky," for USA Records, a small blues label.  Soon after, Dixon convinced her to come audition for the head of Chess Records, Leonard Chess, who signed her immediately.  Ultimately, she'd stay with Chess Records from 1964-1972.
Her first single for Chess was the scorching "I Got What It Takes" (1964), written specifically for her by Dixon.  It's a 3-minute dissertation on why she is the baddest female around, delivered in manner that can only be described as foghorn-like.  (Not even Etta James at her most gritty and lowdown had the same atomic growl that Taylor had.)
And although Taylor is the star here, the backing band is no slouch.  Walter Horton's wailing harmonica and Buddy Guy's plucky lead guitar are the perfect foils for Taylor's vocal.  Then there's Jack Meyers on bass: he's playing at least a half step out of tune, yet it doesn't even matter.  There's something simultaneously immaculate and decadent about the bass being so in the pocket rhythmically yet in the wrong key chromatically.  It simply works in this context.
In short, her Chess debut proves why she earned the title "Queen of the Blues."

"Spoonful" (Howlin' Wolf)

Like a lot of Chester Burnett's (a.k.a. Howlin' Wolf's) output for Chess Records in the 1960s, "Spoonful" (1960) is a composition by writer/arranger/bassist Willie Dixon.  As the liner notes for Howlin' Wolf: The Definitive Collection (2007) state, Burnett himself had penned a number of hits in the 50s and wanted to keep writing and controlling his own output.  However, the owners of Chess Records (brothers Leonard and Phil Chess) saw to it that Dixon, who had a finger on pop tastes and a knack for crafting catchy riffs, was the only one writing new music for Wolf and labelmates like Muddy Waters to keep Chess competitive.  The liner notes from the album include a 60s-era quote from Burnett to music journalist Peter Guralnick: "I can do my own songs better, but, you see, they won't let me."

Even though he wasn't too thrilled about having to sing Dixon's songs (they got in shouting matches quite frequently), Burnett couldn't have asked for a song better suited to his gritty style than "Spoonful," which is loosely based on the recording "A Spoonful Blues" (1929) by Delta bluesman Charlie Patton.

The entire song rides atop a single chord and a shuffling groove as Burnett moans about lustful pursuits and the ends mankind will go to for a mere "spoonful*," his larger-than-life sandpaper baritone duetting perfectly with session guitarist Hubert Sumlin's confident, piercing lead. 
   

(*He ain't singing about a teaspoon, kids.)